River Thames Guide

A
ABAFT - Toward the stern relative to some object ("abaft the fore hatch")
ABEAM — At a right angle to the vessel’s centerline; directly off the side of the ship or boat.
ABOARD - On or within the boat.
ABOUT - To change the course of a boat by tacking; 'ready about' is the order to prepare for tacking.
ABSOLUTE BEARING - The bearing of an object relative to North (true bearing using geographical north or magnetic bearing using magnetic north)
AFT — Toward the stern or rear of a vessel; opposite of forward.
AFLOAT — Floating on the surface of the water; also used to describe a vessel in service or at sea.
AGROUND - Touching or fast to the bottom of the river/lock.
AHEAD — In front of or moving forward of the bow; opposite of astern.
AIS — Automatic Identification System; an electronic tracking system used by ships and coastal stations to exchange navigational data.
ALAFF — An archaic term meaning “to the wind” or “close-hauled,” used in early sailing instructions.
ABOVE DECK - On, not over, the deck.
ALOFT — Up in the rigging, masts, or superstructure of a vessel; above the deck level.
ALONGSIDE — Beside or parallel to a ship or quay; a vessel is said to be alongside when secured to another vessel or dock.
AMIDSHIPS — In the middle portion of a vessel, both lengthwise and athwartships; also a command meaning to center the helm.
ANCHOR — A heavy device attached to a vessel by a cable or chain and dropped to the seabed to prevent drifting.
ANCHORAGE — A designated area where vessels may anchor safely; also the act of anchoring.
ANGLED PLATING — Sloped or chamfered hull plating designed to reduce radar signature or hydrodynamic resistance on modern vessels.
ANTIFOULING — Paint or coating applied to a vessel’s hull to prevent the growth of marine organisms such as barnacles and algae.
APORT - Over to the port side of a vessel.
APPARENT WIND — The wind experienced onboard a moving vessel, resulting from the combination of true wind and the vessel’s motion.
ASTERN — Behind the vessel or moving backward; opposite of ahead.
ATHWARTSHIPS — Across the ship, from side to side, at a right angle to the centreline.
AVAST — A command meaning “stop,” “cease,” or “hold fast”; commonly used in traditional seamanship.
AWASH — Level with or just above the surface of the water; a deck or object awash is intermittently covered by waves.
AWEIGH — Said of an anchor when it has just been lifted clear of the seabed and the ship is free to move.

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B
BALLAST — Weight, usually of lead, iron, or water, placed low in a vessel to provide stability and correct trim.
BARGE — A flat-bottomed vessel used for transporting cargo on rivers and canals, often towed or pushed by a tugboat.
BEACON — A fixed navigation aid, such as a light, buoy, or tower, that marks channels, shoals, or hazards to navigation.
BEAM — The width of a vessel at its widest point; also used to describe directions at right angles to the ship’s centerline (“on the beam”).
BEARING — The direction or angle between an object and the observer’s position, measured in degrees clockwise from north.
BILGE — The lowest interior part of a ship’s hull where water and waste collect; also the term for the curved transition between the bottom and sides of the hull.
BILGE PUMP — A pump used to remove accumulated water from the bilge of a vessel.
BIMINI — A canvas canopy supported by a metal frame over the cockpit or deck, providing shade and weather protection.
BINNACLE - The stand on which a vessel's compass is mounted.
BOLLARD — A sturdy post or fitting on a dock or vessel to which mooring lines are secured.
BOOM — A horizontal spar extending from a mast to control the angle and shape of a fore-and-aft sail.
BOW — The forward end or front of a vessel; opposite of stern.
BOWLINE — A knot forming a fixed loop at the end of a rope, easily untied after loading; known as the “king of knots.”
BOW THRUSTER - A small propeller or water-jet at the bow, used for manoeuvring at slow speed; may be mounted externally or in a tunnel running through the bow from side to side.
BRIDGE — The command center of a vessel where navigation, steering, and communication systems are located.
BRIGHTWORK - Varnished woodwork and/or polished metal.
BRIDLE - A line or wire secured at both ends in order to distribute a strain between two points.
BROADSIDES — The side of a ship above the waterline; also, the simultaneous firing of all guns on one side of a warship.
BUOY — A floating marker anchored to the seabed, used to indicate channels, hazards, or mooring positions.
BULKHEAD — A vertical partition or wall inside a vessel that divides it into compartments, adding structural strength and watertight integrity.
BULWARK — The solid railing or extension of the ship’s side above the deck level, providing protection against the sea.
BUNKER — A compartment for storing fuel oil aboard a ship; “bunkering” refers to refueling a vessel.
BURGEE — A small triangular flag identifying a yacht club or private vessel, flown from the masthead or spreader.

C
CABIN — An enclosed living or sleeping space aboard a vessel, typically for officers or passengers.
CAPSIZE - o turn over.
CAPSTAN — A vertical rotating drum used to wind in ropes, cables, or anchor chains, operated manually or by motor.
CARVEL BUILT — A method of wooden ship construction in which hull planks are fastened edge to edge, creating a smooth outer surface.
CAST OFF - To let go (of mooring lines).
CATAMARAN — A vessel with two parallel hulls connected by a deck or frame, offering high stability and speed.
CHAFING GEAR - Tubing or cloth wrapping used to protect a line from chafing on a rough surface.
CHAIN LOCKER — A compartment in the forward part of a ship where the anchor chain is stowed.
CHANDLER — A merchant or supplier of equipment, provisions, and stores for ships; traditionally called a ship’s chandler.
CHART — A nautical map showing water depths, coastlines, hazards, and navigation aids, used by mariners for safe passage planning.
CHINE — The line or angle where a vessel’s bottom meets its sides; on planing hulls, often sharp to improve lift and reduce drag.
CLEAT — A fitting to which ropes or lines are secured; usually T-shaped or horn-shaped for easy belaying.
CLOVE HITCH — A simple knot used for temporarily securing a rope to a post, spar, or ring.
COAMING — The raised border around a hatch, cockpit, or opening designed to prevent water from entering.
COMPANIONWAY — The staircase or ladder leading from one deck to another on a ship, often protected by a hatch or housing.
COMPASS — A navigation instrument that shows direction relative to the Earth’s magnetic or true north.
COURSE — The direction in which a vessel is steered or intended to travel, measured in degrees clockwise from north.
CROW’S NEST — A lookout platform located high on a mast, providing an elevated view for observing hazards, land, or other ships.
CURRENT — The horizontal movement of water in a particular direction, caused by tides, winds, or differences in salinity and temperature.
CUTLASS BEARING — A water-lubricated bearing supporting a propeller shaft where it exits the hull, lined with rubber or composite material.
CYLINDER BILGE — The rounded part of a ship’s hull where the bottom meets the vertical sides, aiding structural strength and smooth flow through water.

D
DAGGERBOARD — A removable, vertically sliding keel used on small sailing craft to reduce leeway and improve stability.
DAVIT — A small crane or pair of arms used to lower, raise, or support boats, anchors, or other equipment over the ship’s side.
DAYMARK — A fixed navigation aid, often a colored shape or structure, visible by daylight to identify channels or hazards.
DEAD AHEAD — Directly in line with the ship’s bow, 000° relative bearing.
DEAD RECKONING — The process of estimating a vessel’s position by using course, speed, and time from a known point, without external fixes.
DEADWEIGHT — The total weight a ship can safely carry, including cargo, fuel, provisions, and crew.
DECK — A floor or horizontal surface on a vessel that provides structural strength and working space for crew and passengers.
DECKHEAD — The underside of a deck forming the ceiling of the compartment below.
DEEPWATER — Water sufficiently deep for safe navigation; also used to describe ocean-going operations or ships.
DISPLACEMENT — The weight of water displaced by a vessel’s hull when afloat, equal to the vessel’s total weight.
DISTRESS SIGNAL — A recognized signal (visual, radio, or sound) indicating grave and imminent danger and requesting immediate assistance.
DOCK — A structure or enclosed area for the mooring, loading, or repair of ships; also, the act of securing a vessel in such a place.
DOLPHIN — A cluster of piles or a single post used for mooring or as a navigational aid, usually found near piers or channels.
DRAFT — The vertical distance between the waterline and the lowest point of a vessel’s hull; indicates how deeply the vessel sits in the water.
DRAG — Resistance encountered by a vessel moving through water; also the movement of an anchor along the seabed without holding.
DREDGER — A vessel equipped for excavating or clearing sediment from harbors, rivers, or channels to maintain navigable depth.
DRIFT — The sideways movement of a vessel due to wind, current, or tide; also the speed of a current relative to the seabed.
DRY DOCK — A basin that can be drained of water to allow inspection, cleaning, or repair of a ship’s hull below the waterline.
DUFFLE — A sailor’s personal kit or bag; the term originates from the coarse cloth used to make it in the 17th century.

E
EARING - A small line used to fasten the upper corners of a square sail to its yard./div>
EBB - Referring to a receding current./div>
ECHO SOUNDER — An electronic device that measures water depth by timing the return of sound pulses reflected from the seabed.
EIGHT BELLS — The completion of a four-hour watch at sea; also used ceremonially to mark the end of a sailor’s duty or life.
ELEVATION — The vertical angle of a gun barrel or optical instrument relative to the horizontal plane.
EMBARK — To go aboard a ship or to load cargo, passengers, or equipment onto a vessel for a voyage.
ENGINE ROOM — The compartment in which a ship’s main engines and mechanical systems are located.
ENSIGN — A national flag flown by a ship to denote its nationality; naval and civil vessels use distinct ensigns.
ENTRANCE — The forward underwater shape of a vessel’s hull at the bow, affecting its resistance and handling in waves.
EPIRB — Emergency Position-Indicating Radio Beacon; a distress transmitter that sends a vessel’s location to rescue authorities via satellite.
ESCORT — A vessel assigned to accompany and protect another ship or convoy, especially in wartime or hazardous waters.
ESTUARY — The tidal mouth of a river where freshwater mixes with seawater, often navigable by vessels.
EVEN KEEL — A condition where a vessel’s draft is the same fore and aft, indicating a balanced trim.
EXCLUSION ZONE — A restricted area of water established for safety or security around vessels, installations, or operations.
EYE SPLICE — A method of forming a permanent loop at the end of a rope by weaving the strands back into themselves.
EYE OF THE WIND — The exact direction from which the wind is blowing; a sailing vessel cannot sail directly into it.

F
FAIRLEAD — A fitting or ring used to guide a rope, line, or cable in a desired direction, reducing friction and chafing.
FATHOM — A unit of length equal to six feet (1.83 meters), used primarily to measure the depth of water.
FENDER — A cushion or bumper placed between a vessel and a dock or another boat to prevent damage from impact.
FID — A tapered wooden or metal tool used for splicing rope or opening the strands of wire or ropework.
FIGUREHEAD — A carved decorative figure, often of a woman or mythical creature, mounted on the bow of a traditional sailing ship.
FIGURE EIGHT KNOT - A knot in the form of a figure eight, placed in the end of a line to prevent the line from passing through a grommet or a block.
FILLET — A small concave molding or curved reinforcement used in wooden shipbuilding to strengthen joints and reduce stress points.
FLARE — The outward curve of a vessel’s sides above the waterline; also a bright pyrotechnic signal used for distress or illumination.
FLAT — A horizontal surface or deck area aboard a ship; also used to describe shallow coastal waters.
FLEET — A group of ships operating together under one command or for a common purpose; also, to move quickly or lightly over the water.
FLOOD TIDE — The incoming or rising tide; the period between low water and the next high water.
FLUKE — The broad, flat part of an anchor that digs into the seabed to provide holding power.
FOC’S’LE — A contraction of “forecastle”; the forward part of a ship where the crew’s quarters are traditionally located.
FORE — Toward the front or bow of a vessel; opposite of aft.
FOREMAST — The mast nearest the bow on a sailing vessel with two or more masts.
FOREPEAK — The compartment in the extreme forward part of a ship, often used for chain or storage space.
FOULED - Any piece of equipment that is jammed or entangled or dirtied.
FREEBOARD — The vertical distance from the waterline to the upper edge of the deck at the ship’s side; an indicator of how much hull is above water.
FURL — To roll or fold a sail neatly and secure it to its yard, boom, or stay when not in use.
FUSELAGE — The main body of a seaplane or flying boat; included in nautical glossaries due to naval aviation usage.
FUTTOCK — A curved timber forming part of the frame of a wooden ship’s hull, connecting the keel to the upper structure.

G
GAFF — A spar that supports the upper edge of a fore-and-aft sail; also a hook used for landing large fish or handling cargo.
GALLEY — The kitchen or cooking area aboard a ship or boat, equipped for food preparation at sea.
GANGWAY — A movable bridge or ramp used for boarding or leaving a ship; also an opening in the bulwark for access.
GANTLINE — A rope rove through a block, used to hoist or lower tools, gear, or crew aloft; also called a gant rope.
GARBOARD — The strake or plank next to the keel on a wooden vessel; the lowest line of planking in the hull.
GENOA — A large overlapping foresail set on the forestay, extending aft of the mast, used to increase sail area in light winds.
GIG — A light, narrow boat used for transporting officers or crews; also a fast rowing or sailing boat for racing or work.
GIMBAL — A pivoted support allowing an object, such as a compass or lamp, to remain level despite a ship’s rolling and pitching.
GROUND TACKLE — The equipment used to anchor a vessel, including the anchor, chain, cable, and associated fittings.
GUNWALE — The upper edge of a boat’s side; pronounced “gunnel.” Originally “gun ridge” where small cannon were mounted.
GUNPORT — An opening in a ship’s side for a gun or cannon, fitted with a hinged cover to keep out water when closed.
GYBE — To shift the boom of a fore-and-aft sail across the boat when the wind changes direction from one quarter to the other; also spelled “jibe.”
GYROCOMPASS — A compass that uses a fast-spinning gyroscope to find true north rather than magnetic north, unaffected by magnetic deviation.
GALLEON — A large, square-rigged sailing ship of the 16th to 18th centuries, used for trade and war by European powers.
GRAB RAILS - Hand-hold fittings mounted on cabin tops and sides for personal safety when moving around the boat. /div>
GRAPNEL — A small anchor with multiple flukes used for securing small boats, dragging for objects, or retrieving lines.
GRAVING DOCK — A dry dock where vessels are brought for cleaning, inspection, and repairs below the waterline.
GREEN SEA — A large solid wave that breaks over the deck, as opposed to spray or spindrift.
GROUNDING — When a vessel’s hull touches the seabed or shore unintentionally; a minor grounding may not cause damage, but a hard one can breach the hull.
GROUND TACKLE - A collective term for the anchor and its associated gear.
GUN DECK — A deck on a warship where its main battery of guns is mounted; colloquially, a term for any deck below the main deck.

H
HALYARD — A rope or line used for hoisting or lowering a sail, flag, or yard on a vessel.
HARBOR — A sheltered body of water where ships may anchor safely, often equipped with docks, moorings, and facilities for cargo or passengers.
HARD APORT — A helm command meaning to turn the ship’s rudder as far to the port (left) side as possible.
HARD CHINE - An abrupt intersection between the hull side and the hull bottom of a boat so constructed.
HARD OVER — A general command to move the helm or tiller fully to one side; may be qualified as “hard aport” or “hard astarboard.”
HAUL — To pull on a rope or line; a common command aboard sailing vessels meaning to tighten or draw in a line.
HAWSE PIPE — A cylindrical pipe through which an anchor cable passes from the deck to the outside of the hull.
HAWSEHOLE — The opening in a ship’s bow through which an anchor chain or cable passes; also called the hawse.
HAWSE PIPE COVER — A removable plate or fitting used to seal the hawse pipe opening when not in use to prevent water ingress.
HEAD — The toilet or lavatory on a ship; also the forwardmost part of a vessel’s hull.
HEAD SEA — Waves approaching directly from ahead, causing a pitching motion as the ship meets them.
HEADING — The direction in which a vessel’s bow is pointed at any given moment, expressed in degrees relative to north.
HEAVE — To pull or lift using ropes, tackles, or winches; also a command meaning “pull together.”
HEAVE TO — To bring a sailing vessel nearly to a stop by adjusting the sails and rudder to balance wind and sea forces.
HEEL — The temporary inclination of a vessel caused by wind, waves, or turning; distinct from list, which is permanent or static tilt.
HELM — The steering apparatus of a vessel, including the wheel or tiller and associated gear; also the act of steering.
HOIST — To raise or lift a sail, flag, or load using ropes, halyards, or winches; also the section of a flag nearest the hoist line.
HOLD — The space inside a ship’s hull below the decks used for stowing cargo, stores, or ballast.
HULL — The main body of a vessel, including the bottom, sides, and deck, but excluding masts, rigging, and superstructure.
HYDROGRAPHY — The science of surveying and charting bodies of water, including depths, tides, currents, and the sea floor.
HYDROPLANE — A small, fast craft designed to skim along the water’s surface; also a horizontal control surface on submarines for depth control.

I
ICEBREAKER — A specially reinforced vessel designed to break through ice-covered waters and create navigable channels for other ships.
ICING — The accumulation of ice on a ship’s superstructure or rigging due to freezing spray or precipitation, which can affect stability.
IMPELLER — A rotating component of a pump or jet drive that moves water to generate propulsion or cooling flow.
INBOARD — Toward the centerline of a vessel or inside the hull; the opposite of outboard.
INBOARD ENGINE — A marine engine mounted within the hull of the boat, connected to a propeller shaft through a stern gland or drive unit.
INCLINOMETER — An instrument that measures a vessel’s heel or list angle relative to the horizontal plane.
INERTIAL NAVIGATION — A navigation method using gyroscopes and accelerometers to track position without external references such as GPS or stars.
INLET — A narrow waterway or passage connecting a sea, lake, or river with another body of water, often providing access to harbors or lagoons.
INTRACOASTAL WATERWAY — A series of connected rivers, canals, and bays running along a coastline to allow safe navigation within sheltered waters.
IRONCLAD — A 19th-century warship protected by iron or steel armor plating, marking the transition from wooden sailing ships to modern naval vessels.
ISOBAR — A line on a weather chart connecting points of equal atmospheric pressure, used in marine meteorology to forecast winds and storms.
ISOGONIC LINE — A line on a chart connecting points of equal magnetic variation, used to correct compass readings in navigation.
ISOTHERM — A line on a weather map joining points of equal temperature, useful for predicting fog and weather fronts at sea.
ISLAND — A naturally formed area of land surrounded by water and often marked on nautical charts as a navigation reference or hazard.

J
JACK — A national or maritime flag flown from the jackstaff at the bow of a vessel when moored or at anchor.
JACK LINE — A strong line or webbing rigged fore and aft along the deck to which safety harnesses are clipped to prevent falling overboard.
JACKSTAFF — A short flagpole at the bow of a ship or boat from which the national flag (jack) is flown when in harbor.
JACOB’S LADDER — A flexible rope ladder with wooden or metal rungs, used for boarding or climbing aloft.
JAW — The curved fitting at the end of a gaff, boom, or yard that embraces the mast and allows movement while staying attached.
JETTY — A structure extending from shore into the water to protect a harbor or channel and to facilitate the docking of vessels.
JIB — A triangular sail set ahead of the foremast or mainmast, attached to the forestay.
JIBBOOM — A spar extending forward from the bowsprit to carry the outer jib and related rigging.
JIGGER — A small auxiliary sail or mast; on a ketch or schooner, it is the aftermost sail. Also slang for a small tackle or hoisting device.
JINKER — A small coastal trading vessel or lighter, particularly one used on rivers or estuaries (archaic term).
JURY RIG — A temporary or improvised repair to rigging, masts, or gear made at sea after damage.

K
KEEL — The principal structural member of a vessel running lengthwise along the bottom, forming the backbone of the hull and providing stability.
KEELSON — A strong longitudinal beam inside the hull, fastened above the keel to reinforce it and tie the frames together.
KETCH — A two-masted sailing vessel with the smaller mizzen mast located forward of the rudder post, typically rigged for cruising or fishing.
KICKER — A line or tackle used to control the downward tension on a boom; another term for a boom vang.
KNOT — A unit of speed equal to one nautical mile per hour (1.852 km/h).
KNOT - A fastening made by interweaving rope to form a stopper; to enclose or bind an object, to form a loop or a noose; to tie a small rope to an object; or to tie the ends of two small ropes together.
KNOT LOG — A mechanical or electronic device for measuring a vessel’s speed through the water in knots.
KNOTWORK — Decorative ropework or netting made using various knots, often seen in maritime craft or traditional ship decor.
KNUCKLE — The sharp change in a ship’s hull contour, often at the bow or the turn of the bilge; also used to describe a projection on the hull form.
KNOTTER — A sailor skilled in tying, splicing, and working with rope; also an old mechanical speed-measuring device.
KOMBU — A Japanese term used in traditional shipbuilding for kelp or seaweed used as caulking material (archaic).
KRAKEN — A legendary sea monster of Norse mythology said to dwell off the coasts of Norway and Greenland; often symbolically used for great ocean power.

L
LADDER — A means of access between decks or over the ship’s side, constructed of metal, wood, or rope; a “Jacob’s ladder” is a rope version.
LADEN — Loaded with cargo; the opposite of unladen. A “fully laden” vessel is at or near its load line limit.
LAGOON — A shallow body of water separated from the sea by a reef, sandbar, or island, often navigable by small craft.
LANDFALL — The first sighting of land after a voyage; also the point where a ship or aircraft reaches land from the sea.
LANDING STAGE — A platform or pontoon where passengers or cargo are embarked or disembarked from boats or ships.
LANYARD — A short rope or cord used for securing, hanging, or operating gear such as whistles, knives, or signal flags.
LASHING — A rope or line used to tie or secure equipment or cargo firmly in place.
LATITUDE — The angular distance of a place north or south of the equator, measured in degrees; used to determine position in navigation.
LAUNCH — To send a vessel into the water; also a type of open powerboat or tender used for ferrying passengers and supplies.
LAZARETTE - A storage space in a boat's stern area.
LEE — The side of a vessel or object sheltered from the wind; opposite of windward.
LEEWAY — The sideways drift of a vessel downwind from its intended course due to the force of the wind on its hull or superstructure.
LIFELINE — A safety line or cable rigged along the deck or side of a vessel to prevent crew from falling overboard.
LIGHTHOUSE — A tall structure fitted with a powerful light and other signals to guide mariners and mark dangerous areas of coast.
LIGHTSHIP — A moored vessel equipped with a beacon light and fog signals, stationed where building a lighthouse is impractical.
LINE — A general term for rope or cordage when used aboard ship; specific lines are named by purpose, such as halyard or sheet.
LIST — The inclination or tilt of a vessel to one side due to uneven loading or flooding.
LOG — A record of a ship’s daily progress, courses, and events; originally a wooden log thrown overboard to measure speed through the water.
LONGITUDE — The angular distance of a place east or west of the prime meridian at Greenwich; used with latitude to determine position.
LOOKOUT — A crew member assigned to keep watch for other vessels, obstacles, or hazards to navigation.
LUFF - The forward edge of a sail. To luff up is to turn the boat's head right into the wind.
LUBBER'S LINE - A mark or permanent line on a compass indicating the direction forward parallel to the keel.

MAGNETIC COMPASS — A navigation instrument using the Earth’s magnetic field to indicate direction relative to magnetic north.
MAGNETIC VARIATION — The angular difference between true north and magnetic north, varying by geographic location and time.
MAIN DECK — The principal deck of a vessel, running the full length of the hull and forming its structural strength member.
MAINFRAIL — The top edge or rail of a bulwark or parapet along a ship’s deck (archaic term).
MAINSAIL — The principal sail on the mainmast of a sailing vessel.
MARLINSPIKE - A tool for opening the strands of a rope while splicing.
MAST — A vertical spar that supports sails, rigging, antennas, or navigation lights on a vessel.
MEAN LOW WATER — The average height of all low tides over a standard 19-year period, used as a chart datum for depth measurements.
MESS DECK — The deck or compartment where crew members eat and gather off duty.
MIDSHIP — The middle portion of a vessel, both lengthwise and athwartships; also used as a steering command meaning to center the rudder.
MOORING — The act of securing a vessel to a fixed object such as a dock, buoy, or anchor; also the equipment used for that purpose.
MOTOR SAILER — A vessel equipped for both sailing and powered propulsion, designed for efficiency in either mode.
MUSTER — To assemble crew or passengers, especially for inspection or emergency drills.
MUTINY — An uprising or rebellion by a ship’s crew against lawful authority on board.
MYLAR — A durable, low-stretch polyester film used in high-performance sails for strength and shape retention.

N
NACELLE — A streamlined housing for machinery, such as an engine or generator, mounted externally on a vessel or craft.
NARROW BOAT - a craft of limited width designed to go through smaller canal locks.
NAUTICAL MILE — A unit of distance used in navigation equal to one minute of latitude, or 1,852 meters (about 1.15 land miles).
NAVAL ARCHITECT — A professional engineer who designs and constructs ships and other floating structures.
NAVIGATION — The science and practice of plotting, directing, and controlling the movement of a vessel from one place to another safely.
NAVIGATION LIGHTS — The colored lights displayed by vessels to indicate their position, direction, and status at night or in poor visibility.
NAVY — A nation’s organized maritime armed forces; collectively, its warships and supporting vessels.
NEAP TIDE — A tide of least range occurring twice a month when the sun and moon are at right angles relative to the earth.
NEEDLE BEARING — A type of roller bearing with long, thin rollers used in marine machinery for compact, low-friction support.
NEEDLE GUN — A type of bolt-action firearm once used by naval forces; term sometimes used for deck tools with multiple chiseling pins.
NESTED BOATS — Small boats stowed one inside another to save space aboard ship.
NET TONNAGE — A measure of a vessel’s usable internal volume after deducting non-revenue spaces, used for port fees and registration.
NIP — The point where a rope or cable passes around a block, spar, or fairlead; also the pinch point that bears friction under strain.
NIPPER — A short rope used to temporarily fasten the messenger to an anchor cable when weighing anchor; also a junior sailor or boy seaman (archaic).
NOON SIGHT — A celestial navigation observation of the sun’s altitude at its highest point to determine latitude.
NOR’EASTER — A strong storm or wind blowing from the northeast, common along the Atlantic coasts.
NOTICE TO MARINERS — Official updates issued to correct and maintain nautical charts and publications for safe navigation.

O
OAR — A long pole with a flat blade used to propel or steer a boat by rowing.
OARLOCK — A pivoting device fixed to the gunwale or side of a boat to hold an oar in place while rowing; also called a rowlock.
OBSTRUCTION — Any object, natural or man-made, that restricts safe navigation, such as rocks, wrecks, or buoys.
OFFING — The part of the sea visible from shore but far enough away to be clear of coastal dangers; a ship “in the offing” is nearby but not yet in port.
ON THE BEAM — A direction at right angles to the vessel’s centerline; an object “on the beam” lies directly abeam.
ON THE ROCKS — A colloquial expression meaning aground on rocks; also used figuratively for a ship or venture in trouble.
OUTBOARD — Away from the centerline of a vessel; also refers to an external motor mounted on the stern of a small boat.
OUTHAUL — A line or tackle used to stretch the foot of a sail along a boom to control its shape and tension.
OVERBOARD — Over the side of a vessel into the water; to “go overboard” means to fall or jump into the sea.
OVERHAUL — To examine and repair equipment thoroughly; also to overtake another vessel at sea.
OVERHEAD — The ceiling or upper interior surface of a compartment below decks.
OVERTAKING VESSEL — A vessel approaching another from more than 22.5 degrees abaft the beam; required by navigation rules to keep clear.
OWNER’S FLAG — A personal or company flag flown to indicate ownership of a vessel, often at the mainmast or spreader.
OXTER — The curved part of a vessel’s side where it meets the sternpost; also the shoulder of the stern.

P
PAINTER — A rope attached to the bow of a small boat, used for securing or towing it.
PALM — A leather hand guard fitted with a metal eye used by sailmakers to push needles through heavy canvas when sewing.
PARBUCKLE — A rope sling or loop used to roll casks or barrels up or down an incline.
PARREL — A rope or fitting that secures a yard, gaff, or boom to a mast, allowing it to move up or down while remaining attached.
PARTING — The breaking of a line, cable, or hawser under strain; a serious event when mooring or towing.
PASSAGE — A voyage or transit from one place to another, especially between ports or along a river or channel.
PATCH — A repair applied to a sail, hull, or other surface to close a tear or hole temporarily or permanently.
PAY OUT — To gradually release or slacken a rope, chain, or cable under control.
PEAK — The upper aft corner of a gaff sail; also the highest point of a wave or tide cycle.
PILOT — A person qualified to guide ships into or out of harbors or through difficult waters; also a small guide vessel.
PITCH — The rise and fall motion of a vessel’s bow and stern in waves; also the twist or angle of a propeller blade.
PLANING — When a boat’s hull rises and skims over the surface of the water at high speed, reducing drag.
PORT — The left-hand side of a vessel when facing forward; also a harbor or place where ships load and unload.
PORTAGE — In inland or river navigation, portage refers both to the process and the route carrying a boat and its cargo overland between two bodies of water, or around an obstacle such as a lock, weir, waterfall or dam.
PORTLIGHT — A circular or rectangular window in a ship’s side, commonly called a porthole.
PROPELLER — A rotating device with blades that drives a vessel through the water by thrust.
PROW — The foremost part of a vessel’s bow above the waterline; the projecting front of the ship.
PUMPROOM — A compartment on a ship housing pumps and related machinery, especially on tankers.
PURSER — An officer responsible for accounts, provisions, and stores aboard a ship; now often called the supply officer.
PYLON — A tall structure or mast used for mounting navigation lights, antennas, or signal equipment near waterways.

Q
QUADRANT — A quarter-circle instrument formerly used in celestial navigation to measure the altitude of celestial bodies before the sextant was invented.
QUARTER — The sides of a ship toward the stern; also a term for dividing the crew into watches or duty stations.
QUARTERDECK — The part of a ship’s upper deck reserved for officers and ceremonial functions; traditionally the place of the ship’s ensign and salute.
QUARTERING SEA — Waves approaching a vessel from a direction between the beam and the stern, often causing rolling and yawing.
QUARTERMASTER — A petty officer or rating responsible for navigation, steering, and maintaining the ship’s compass and charts.
QUICK FLASHING LIGHT — A navigational aid light that flashes more than 50 times per minute, used to mark specific hazards or channel entrances.
QUOIN — A wedge-shaped block used to adjust the elevation of a gun barrel on old sailing ships.
QUOINING — The act of securing or bracing barrels or cargo by wedges to prevent movement at sea.
QUOIN PORT — An opening in a ship’s side for loading guns or cargo, fitted with a hinged cover for weather protection.
QUOIT — A small metal or rope ring thrown over a peg in a deck game popular among sailors during long voyages.
QUEEN’S HARBOUR MASTER — The official in charge of port operations and navigation control in Royal Navy or government-controlled harbors.
QUEENSHIP — A ceremonial or honorific title sometimes used for a ship of special prestige or flagship status (e.g., RMS Queen Mary).
QUEEN’S COLOUR — A ceremonial flag carried by Royal Navy or Commonwealth naval units, symbolizing loyalty to the Crown.
QUEEN’S REGULATIONS — The code of regulations and orders governing discipline and conduct in the Royal Navy.

R
RADAR — Radio Detection and Ranging; an electronic system that uses reflected radio waves to detect and measure the position of objects.
RADAR REFLECTOR — A device fitted to small boats or buoys to improve their visibility on radar by reflecting radar signals back to their source.
RAIL — The upper edge of a ship’s side or bulwark; also any protective or decorative guard along the deck edge.
RANGE LIGHTS — Two fixed navigation lights of different heights that, when aligned vertically, indicate the correct channel course to steer.
RATLINES — Small ropes secured across the shrouds to form steps for climbing the rigging.
RED ENSIGN - the flag of British registered civilian vessels (red with a Union Flag in upper left corner)
REEF — To reduce the area of a sail by folding or rolling part of it; also a ridge of rock, coral, or sand near the surface of the water.
REEFER — A refrigerated cargo ship; also a slang term for a sailor’s short double-breasted jacket.
REEL — A drum or spool used to wind and store lines, cables, or hoses on deck.
REGATTA — A series of boat or yacht races, often part of a social or sporting event.
RIG — The arrangement of masts, sails, and rigging on a sailing vessel; as a verb, to set up or equip with ropes and spars.
RIGGING — The system of ropes, wires, or chains that support a vessel’s masts (standing rigging) and control its sails (running rigging).
RIP CURRENT — A strong, narrow current flowing seaward from near the shore, often through surf zones or between sandbars.
ROPE — A length of cordage made from twisted or braided fibers; aboard ship, specific ropes have different names once in use (e.g. halyard, sheet, painter).
RUDDER — A flat, movable surface at the stern used to steer a vessel, controlled by a wheel or tiller.
RUNNING LIGHTS — The navigation lights displayed by vessels underway at night to indicate their position and heading.
RUTTER — An old term for a mariner’s sailing directions or pilot book containing coastal routes and landmarks.

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S
SALOON — The main cabin or lounge area of a yacht or passenger vessel, used for dining or relaxation.
SALOON DECK — The deck on which the main passenger lounge or saloon is located, usually amidships.
SCOPE - The ratio of length of anchor rode in use to the vertical distance from the bow of the vessel to the bottom of the river; usually six to seven to one.
SCUPPER — A drainage opening in the deck, bulwark, or cockpit that allows water to run overboard.
SCREW — The propeller of a ship; the term “screw steamer” refers to vessels driven by propellers rather than paddles.
SCUPPER HOSE — A flexible tube or fitting connected to a scupper to direct drainage overboard below deck level.
SEACOCK — A valve in the hull of a vessel used to control the intake or discharge of water through a through-hull fitting.
SEAMAN — A sailor; a member of a ship’s crew below the rank of officer; also a rating in naval service.
SEAWORTHY — In a condition fit for safe navigation; structurally sound and properly equipped for its intended voyage.
SECURE — To make fast or safe; to tie down, lock, or stow equipment and gear properly before getting under way.
SET AND DRIFT — “Set” is the direction of a current; “drift” is the speed of that current. Both are used in navigation calculations.
SHIP — A large seagoing vessel; also, in the broad sense, any craft used for transportation on water. As a verb, to put on board or take to sea.
SHIPMATE — A fellow member of the same ship’s crew; a friendly term among sailors.
SHIPSHAPE — Neat, orderly, and in proper condition; derived from the phrase “shipshape and Bristol fashion.”
SOUNDING — The act of measuring the depth of water under a vessel, originally with a lead line, now often by echo sounder.
STARBOARD — The right-hand side of a vessel when facing forward, opposite of port.
STERN — The rear or aft-most part of a vessel; opposite of bow.
STERN LINE — A mooring line leading aft from the vessel to the dock or quay.
STOW — To pack or secure items safely for sea; properly arranging gear and equipment below decks.
SWELL — The broad, smooth, rolling waves that continue after the wind has died down, usually generated by distant weather systems.
SWIVEL — A fitting that allows a chain, line, or cable to turn freely without twisting.

T
TACK — The lower forward corner of a sail; also the course of a sailing vessel with respect to the wind (e.g. on the port tack or starboard tack).
TACKLE — An arrangement of ropes and blocks used to gain mechanical advantage for lifting or pulling heavy loads.
TAFFRAIL — The rail around the stern of a ship, often forming the upper edge of the bulwark or deck at the stern.
TAUT — Describes a rope, cable, or line under tension; opposite of slack.
TELEMETER — A device used for measuring distance to an object, sometimes part of a ship’s range-finding or fire-control system.
TENDER — A small boat used to service or transport people and supplies to and from a larger vessel at anchor.
THWART — A crosswise seat or brace in a small boat, often serving as a rowing bench or hull stiffener.
TIDE — The periodic rise and fall of sea level caused by the gravitational pull of the moon and sun.
TILLER — A lever attached to the rudder head for steering a small boat manually.
TOPSIDES — The portion of a boat’s hull above the waterline; also the upper deck and visible outer structure.
TRANSOM — The flat or slightly curved surface forming the stern of a boat, where an outboard motor may be mounted.
TRIM — The fore-and-aft balance of a vessel; also the adjustment of sails, ballast, or load to maintain correct attitude in the water.
TRIMARAN — A multihull vessel with a main hull and two smaller outrigger hulls for stability and speed.
TRUNNION — A cylindrical projection on each side of a cannon or gun mount, allowing it to pivot in elevation.
TUG — A small but powerful vessel used to tow or push larger ships, barges, or floating structures in harbors and channels.

U
UNDER WAY — A vessel that is not at anchor, aground, or made fast to the shore; moving through the water under its own power or sail.
UNDERTOW — A subsurface current moving seaward after waves break on the shore; can be dangerous to swimmers near beaches or river mouths.
UNIFORM — The NATO phonetic alphabet word for the letter “U.” In flag signalling, the Uniform flag means “You are running into danger.”
UNLADEN — Without cargo; a vessel that has discharged its load and is sailing in ballast or empty.
UPPERWORKS — The parts of a ship’s hull and structure above the waterline, including decks, superstructure, and fittings.
UPWELLING — The vertical movement of cold, nutrient-rich water from deeper layers to the surface, often influencing coastal currents.
UTILITY BOAT — A small general-purpose boat carried aboard larger ships, used for transport, rescue, or maintenance duties.
UTMOST — A nautical expression meaning the greatest extent or highest degree of effort, often in phrases like “do one’s utmost.”
UTC — Coordinated Universal Time, the world’s primary time standard used in navigation, equivalent to Zulu Time (Z).

V
V-BERTH — A V-shaped sleeping area located in the forward part of a boat, between the hull sides at the bow.
V-BOTTOM — A hull design with a pronounced V shape along the keel, giving good performance and stability in choppy water.
VANG — A rope, tackle, or hydraulic device used to control the angle or tension of a boom or gaff; also called a boom vang.
VARIATION — The angular difference between true north and magnetic north; used in compass corrections for navigation.
VEER — To let out more cable or rope; also means a change in wind direction clockwise in the northern hemisphere.
VENTILATOR — A fitting used to circulate air below decks, often mushroom- or cowl-shaped.
VESSEL — Any craft designed to navigate on water, including boats, ships, and barges.
VHF RADIO — Very High Frequency radio used for marine communication between ships, ports, and coastguard stations.
VICTOR — The NATO phonetic alphabet word for the letter “V.” In flag signalling, the Victor flag means “I require assistance.”
VIZ. — Nautical abbreviation of the Latin word “videlicet,” meaning “namely” or “that is to say,” used in log entries and charts.
VOYAGE — A journey or passage by sea from one port or place to another.

W
WAKE — The disturbed track of water left behind a moving vessel, caused by its hull and propeller action.
WATCH — A duty period for part of a ship’s crew, typically four hours; also the group assigned to that period.
WATERLINE — The line where the hull of a vessel meets the surface of the water; used as a reference for loading and trim.
WATERWAY — A navigable channel, river, or passage used by vessels; also the gutter along a ship’s deck edge for drainage.
WAY — The movement of a vessel through the water; a ship “has way” when it is moving, and “dead in the water” when it is not.
WEATHER SIDE — The side of a ship or object facing the wind; opposite of the lee side.
WELL-DECK — A lower deck area between raised forecastle and quarterdeck, often exposed to the weather.
WHEELHOUSE — The enclosed area from which a vessel is steered and navigated; also called the pilothouse.
WINDWARD — The direction from which the wind is blowing; opposite of leeward.
WORMING — Filling the grooves between the strands of a rope with small cords before serving, to make it smooth and watertight.
WRECK — The remains of a vessel that has been destroyed, stranded, or sunk; also used as a verb meaning to ruin or destroy.
WRONG WAY — Term used to warn that a vessel is moving astern or against the intended direction of traffic.

X
X-BRACE — A cross-shaped structural support used in shipbuilding or mast design to increase rigidity and resist torsion.
X-BOW — A modern inverted bow design (pioneered by Ulstein) that improves fuel efficiency, reduces pitching, and provides a smoother ride in heavy seas.
X-ROPE — A crossing or braided rope arrangement used for securing or rigging where extra strength or reduced stretch is needed.
X-Y COORDINATES — A method of plotting positions on electronic or paper charts, where “X” represents longitude and “Y” represents latitude in navigation systems.
XENON LAMP — A type of high-intensity discharge light used in searchlights and signalling lamps aboard ships.
X-RAY — The NATO phonetic alphabet word for the letter “X.” Also used in signalling and naval communication (e.g. “Flag X-ray” for special instructions).

Y
YACHT — A vessel used for pleasure or sport, usually powered by sails or engines, ranging from small craft to large luxury ships.
YARD — A horizontal spar on a mast from which a square sail is set; also a term for certain dock or shipyard areas.
YARDARM — The outer end of a yard, from which signal flags or ceremonial items may be hung; “sun over the yardarm” means time for a drink.
YAW — A side-to-side motion of a vessel’s bow, often caused by wind or waves; to “yaw” is to swing off course temporarily.
YAWL — A two-masted sailing vessel with a small mizzen mast located aft of the rudder post, used for cruising or working boats.
YAWNING — A vessel’s tendency to swing widely from side to side when towing or in heavy seas.
YEOMAN — A naval rating responsible for clerical duties, signals, and communication records aboard ship.
YOKE — A device used to connect twin rudders or control lines, or the crossbar on a ship’s wheel that turns the rudder.
YONDER — Nautical or sailor’s expression meaning “over there” or “in that direction.”
YOUNG SEA — A sea state in which waves are still being generated by the wind and have not yet reached full maturity or regular pattern.

Z
Z-DRIVE — A type of azimuth thruster propulsion system with shafts in a ‘Z’ configuration, allowing 360° rotation for precise maneuvering.
ZEBRA — NATO phonetic for “Z.” In U.S. Navy usage, “Condition Zebra” means full watertight integrity (all hatches closed).
ZENITH — The point in the sky directly above the observer; important in celestial navigation when using a sextant.
ZEPHYR — A light, gentle breeze, often from the west; used poetically in weather descriptions at sea.
ZIG-ZAG — A defensive ship maneuver with alternating course changes to evade detection or torpedoes.
ZODIAC — A make of rigid inflatable boat (RIB), now a generic term for similar tenders or rescue craft.
ZONE TIME (ZT) — Local mean time for a ship’s time zone, used for navigation and log entries.
ZULU TIME (Z) — Coordinated Universal Time (UTC), the standard time reference for navigation and radio communication.
ZUMMAN — Old seafaring slang for a shipmate or seaman (archaic term from West Country dialect).

Nautical Glossary