MarineHeading / course over ground
Heading describes where the bow points; course over ground describes the direction of movement over the Earth.
Read the definitions →MARINEBRANDS / REFERENCE DESKKnow the term.
Know the term.
Understand the difference.
A practical marine glossary for reading specifications, discussing upgrades and making sense of life on the water.
A—Z108
TERMS · NINE TOPICS
SAILING / FISHING / POWER
Original MarineBrands explanations · Reviewed 5 October 2026 · Australian English, with common alternative spellings and acronyms.
Similar words. Different jobs.
EPIRB / PLB / AIS MOB
Vessel beacons, personal beacons and local AIS locating functions have different roles and requirements.
Read the definitions →Working load / breaking load
A permitted working rating is not the same as the load associated with failure in a test.
Read the definitions →Cavitation / ventilation
Vapour cavities and air entering propeller flow are different mechanisms.
Read the definitions →108 of 108 terms
Electronics & networks# Link to term
AIS
Also find under: automatic identification system
Automatic Identification System: a radio-based system exchanging vessel identity, position and other data.
In practice
Topic references & further reading ↗Receiving AIS targets does not mean your own vessel transmits, or that every nearby vessel is represented.
Safety & communications# Link to term
AIS MOB
Also find under: man overboard beacon person overboard beacon
An AIS-based person-overboard locating device that broadcasts to compatible nearby receiving equipment.
In practice
Topic references & further reading ↗An AIS locating function is distinct from satellite distress alerting; some products combine functions.
Weather, tides & anchoring# Link to term
Anchor rode
Also find under: rode
The chain, rope or combination connecting the vessel to its anchor.
In practice
Topic references & further reading ↗A rode description should identify the components and their compatibility with the anchoring equipment.
Sails & sailing# Link to term
Apparent wind
Also find under: AWA AWS
The wind experienced aboard a moving vessel, combining the ambient wind with the effect of vessel motion.
In practice
Topic references & further reading ↗An instrument showing apparent wind is not displaying the same quantity as true wind.
Electronics & networks# Link to term
Backbone
Also find under: network backbone
The main trunk of an NMEA 2000 network to which device connections are made.
In practice
Topic references & further reading ↗A network drawing should distinguish the backbone from each device’s drop cable.
Boat anatomy & directions# Link to term
Beam
Also find under: width
The width of a vessel, usually its maximum width when given as a principal dimension.
In practice
Topic references & further reading ↗Confirm whether a published beam includes projecting fittings when planning a berth or transport.
Navigation & charts# Link to term
Bearing
Also find under: BRG
The direction from one position towards another, expressed against a stated reference.
In practice
Topic references & further reading ↗Check whether a bearing is true, magnetic or relative before comparing numbers.
Rigging & deck hardware# Link to term
Block
Also find under: pulley
A fitting containing one or more sheaves that guide a line.
In practice
Topic references & further reading ↗Check line size, load rating and mounting orientation; outer size is not a load specification.
Boat anatomy & directions# Link to term
Bow
Also find under: front
The forward end of a vessel.
In practice
Topic references & further reading ↗Describe a mounting position relative to the bow rather than the direction you happen to be facing.
Rigging & deck hardware# Link to term
Breaking load
Also find under: break load
The load associated with failure in a specified test or rating convention.
In practice
Topic references & further reading ↗It is not a safe operating target; the test basis and manufacturer’s working guidance matter.
Engines & propulsion# Link to term
Cavitation
Formation and collapse of vapour cavities where local liquid pressure falls sufficiently low.
In practice
Topic references & further reading ↗Air entering a propeller is ventilation, a different mechanism that may produce similar symptoms.
Navigation & charts# Link to term
Chart datum
Also find under: CD
The reference level from which charted depths and related tidal heights are measured.
In practice
Topic references & further reading ↗Confirm that tide information and the chart use compatible references before comparing them.
Fishing & sonar# Link to term
CHIRP
Also find under: compressed high intensity radiated pulse
A sonar transmission method that sweeps through a range of frequencies within a pulse.
In practice
Topic references & further reading ↗It describes the signal method, not a complete guarantee of image quality for a given installation.
Sails & sailing# Link to term
Clew
The corner where the foot and leech meet on a conventional triangular sail.
In practice
Topic references & further reading ↗Provide a photograph of the clew attachment when discussing a replacement sail or fitting.
Navigation & charts# Link to term
Course over ground
Also find under: COG
The direction of the vessel’s movement over the Earth’s surface.
In practice
Topic references & further reading ↗A GNSS-derived course describes motion, so it should not be assumed to equal bow direction.
Boat anatomy & directions# Link to term
Displacement
Also find under: boat displacement
The mass of water displaced by a floating vessel, equal to the vessel’s mass in that condition.
In practice
Topic references & further reading ↗Compare light and loaded displacement on the same basis when reviewing boat specifications.
Fishing & sonar# Link to term
Down-scanning sonar
Also find under: down imaging downscan
Sonar producing a detailed view of returns beneath the vessel using a suitable system.
In practice
Topic references & further reading ↗Do not assume that a display supporting the feature includes the necessary transducer in every bundle.
Boat anatomy & directions# Link to term
Draft
Also find under: draught
The vertical distance from the waterline to the lowest underwater part of the vessel.
In practice
Topic references & further reading ↗Loading and appendages affect draft; a brochure figure needs its stated condition.
Fishing & sonar# Link to term
Drag
Also find under: reel drag
A reel mechanism that permits line to leave the spool under controlled resistance.
In practice
Topic references & further reading ↗Drag is a reel function; it is not the same as the line’s breaking strength.
Electronics & networks# Link to term
Drop cable
Also find under: drop lead
The branch cable linking an NMEA 2000 device to the backbone.
In practice
Topic references & further reading ↗Record the branch arrangement when asking an installer to expand a network.
Safety & communications# Link to term
DSC
Also find under: digital selective calling
Digital Selective Calling: a system for sending digital calls, including distress alerts, over marine radio.
In practice
Topic references & further reading ↗A DSC-capable radio still needs the appropriate setup, position input and user knowledge.
Safety & communications# Link to term
EPIRB
Also find under: emergency position indicating radio beacon
Emergency Position Indicating Radio Beacon: a maritime distress beacon designed for vessel use.
In practice
Topic references & further reading ↗Check the exact model, registration and applicable carriage requirements; brand names alone do not establish suitability.
Electronics & networks# Link to term
Firmware
Also find under: software update
Software embedded in a device that controls its operation.
In practice
Topic references & further reading ↗Record exact device and firmware versions when reporting a compatibility problem.
Sails & sailing# Link to term
Foot
The lower edge of a sail.
In practice
Topic references & further reading ↗The foot measurement alone does not specify the complete sail shape or attachment arrangement.
Boat anatomy & directions# Link to term
Freeboard
The vertical distance between the waterline and a specified deck edge or upper side reference.
In practice
Topic references & further reading ↗Ask where a quoted freeboard was measured; it is not the same dimension as draft.
Sails & sailing# Link to term
Furling
Also find under: furler
Rolling or gathering a sail for stowage, or for area reduction where the system permits it.
In practice
Topic references & further reading ↗Not every furling arrangement is suitable for sailing with a partly furled sail.
Engines & propulsion# Link to term
Gear ratio
Also find under: reduction ratio
The specified relationship between input and output rotational speeds in a transmission.
In practice
Topic references & further reading ↗Check the maker’s ratio convention when matching an engine, gear and propeller.
Electronics & networks# Link to term
GNSS
Also find under: global navigation satellite system
Global Navigation Satellite System: the general term for satellite systems used to determine position and related information.
In practice
Topic references & further reading ↗GPS is one GNSS constellation; a receiver may use more than one system.
Electronics & networks# Link to term
GPS
Also find under: global positioning system
Global Positioning System, the United States satellite-navigation system.
In practice
Topic references & further reading ↗A product described casually as a GPS may actually combine receiver, chart display and other functions.
Sails & sailing# Link to term
Gybing
Also find under: jibing gybe jibe
Changing tack with the stern passing through the wind direction, transferring the sail across.
In practice
Topic references & further reading ↗Also spelled jibing. The term is distinct from tacking and does not describe a safe procedure by itself.
Sails & sailing# Link to term
Halyard
A line used to hoist a sail, flag or similar item.
In practice
Topic references & further reading ↗A halyard specification should identify its job, length and the hardware through which it runs.
Navigation & charts# Link to term
Heading
Also find under: HDG
The direction in which the vessel’s bow points, expressed against a stated north reference.
In practice
Topic references & further reading ↗Heading can differ from the path over the seabed when current or leeway acts.
Engines & propulsion# Link to term
Inboard
Also find under: inboard engine
An engine installed within the vessel, with power transmitted to a propulsion arrangement.
In practice
Topic references & further reading ↗The word identifies engine location, not whether the boat has a shaft, saildrive or another drive.
Safety & communications# Link to term
Inflatable lifejacket
A lifejacket whose buoyancy depends on inflation of a chamber by its specified mechanism.
In practice
Topic references & further reading ↗Inspection, servicing and rearming requirements depend on the exact model and use.
Fishing & sonar# Link to term
Jigging
A fishing method using an animated lure or jig, often worked through repeated lifts and drops.
In practice
Topic references & further reading ↗This names a method, not permission to use a particular rig in a particular waterway.
Safety & communications# Link to term
Kill cord
Also find under: engine stop lanyard safety lanyard
A cord linking an operator to an engine-stop arrangement so separation can trigger the stop function.
In practice
Topic references & further reading ↗Fit and use the actual craft’s system according to its instructions; this definition is not a substitute for that procedure.
Weather, tides & anchoring# Link to term
Knot
Also find under: kn knots kt
A speed of one nautical mile per hour.
In practice
Topic references & further reading ↗A knot is a speed unit here, not a rope fastening. Ten knots means ten nautical miles per hour.
Navigation & charts# Link to term
Latitude
Also find under: lat
Angular position north or south of the equator.
In practice
Topic references & further reading ↗Keep the hemisphere and coordinate format when passing a position to someone else.
Fishing & sonar# Link to term
Leader
Also find under: fishing leader
A length of fishing line between the main line and the terminal tackle.
In practice
Topic references & further reading ↗Select the material and connection for the intended method; its stated strength is not the whole setup’s strength.
Sails & sailing# Link to term
Leech
The after edge of a conventional fore-and-aft sail.
In practice
Topic references & further reading ↗Tell a sailmaker where along the leech any flutter or damage appears.
Boat anatomy & directions# Link to term
Length overall
Also find under: LOA
The vessel’s overall length under the measurement convention being used.
In practice
Topic references & further reading ↗Ask whether bowsprits, platforms or other projections are included before booking space.
Safety & communications# Link to term
Lifejacket
Wearable flotation equipment designed to help support a person in the water under its specified performance class.
In practice
Topic references & further reading ↗Choose and maintain the appropriate type and fit; a glossary cannot determine the legal requirement for every activity.
Fishing & sonar# Link to term
Live sonar
Also find under: live scanning sonar
A product category providing rapidly updated underwater views of a selected area.
In practice
Topic references & further reading ↗Compare aiming, mounting, compatible equipment and training rather than treating live as a standardised performance rating.
Navigation & charts# Link to term
Longitude
Also find under: lon long
Angular position east or west of the reference meridian.
In practice
Topic references & further reading ↗Minutes and decimal degrees are different formats; copy the complete position convention.
Sails & sailing# Link to term
Luff
The forward edge of a conventional fore-and-aft sail; also a verb describing sail flutter or turning towards the wind.
In practice
Topic references & further reading ↗State whether you mean the sail edge or a handling action when describing a problem.
Safety & communications# Link to term
MMSI
Also find under: maritime mobile service identity
Maritime Mobile Service Identity: an identifying number used in maritime radio and related systems.
In practice
Topic references & further reading ↗Use the correct assigned identity when configuring eligible equipment; do not invent a number.
Electronics & networks# Link to term
Multifunction display
Also find under: MFD chartplotter
A screen and processing unit that presents several marine functions through one interface.
In practice
Topic references & further reading ↗Check which functions need external sensors, modules, subscriptions or compatible network equipment.
Navigation & charts# Link to term
Nautical mile
Also find under: NM nmi
A unit of distance equal to 1,852 metres.
In practice
Topic references & further reading ↗Keep nautical miles separate from land miles when reading ranges or planning distances.
Weather, tides & anchoring# Link to term
Neap tide
A tide occurring in the part of the cycle generally associated with smaller tidal ranges.
In practice
Topic references & further reading ↗Neap does not mean no tidal movement, current or navigational risk.
Electronics & networks# Link to term
NMEA 0183
Also find under: NMEA0183
A marine serial-data standard used by many instruments and navigation devices.
In practice
Topic references & further reading ↗It is not directly interchangeable with NMEA 2000; interfacing requires the appropriate arrangement.
Electronics & networks# Link to term
NMEA 2000
Also find under: N2K NMEA2000
A marine communications standard used to exchange supported data between compatible devices on a network.
In practice
Topic references & further reading ↗Shared connectors do not guarantee that every desired data item or control function is supported.
Engines & propulsion# Link to term
Outboard
Also find under: outboard motor
A propulsion unit mounted externally that commonly combines engine, transmission and lower drive assembly.
In practice
Topic references & further reading ↗Check the boat’s approved installation and the complete model specification, not only advertised power.
Safety & communications# Link to term
PFD
Also find under: personal flotation device
Personal flotation device, a broad term used for wearable flotation equipment.
In practice
Topic references & further reading ↗Check the actual standard, performance level and intended use rather than relying on the acronym alone.
Electronics & networks# Link to term
PGN
Also find under: parameter group number
Parameter Group Number: an identifier for a data message group in NMEA 2000.
In practice
Topic references & further reading ↗Check the supported send and receive PGNs for the particular information you want to exchange.
Boat anatomy & directions# Link to term
Planing
A running condition in which hydrodynamic lift supports a substantial part of a hull’s weight.
In practice
Topic references & further reading ↗A planing description does not establish comfortable performance in a particular sea state.
Safety & communications# Link to term
PLB
Also find under: personal locator beacon
Personal Locator Beacon: a portable distress beacon intended to be carried by an individual.
In practice
Topic references & further reading ↗A PLB is not automatically an acceptable replacement for a vessel’s required EPIRB.
Boat anatomy & directions# Link to term
Port
Also find under: port side
The vessel’s left side when facing towards its bow.
In practice
Topic references & further reading ↗The port side stays the same when a crew member turns around.
Engines & propulsion# Link to term
Power
Also find under: kW horsepower hp
The rate of doing work; engine output is commonly stated in kilowatts or a specified horsepower unit.
In practice
Topic references & further reading ↗Confirm the unit and rating standard before comparing two advertised engine numbers.
Engines & propulsion# Link to term
Propeller pitch
Also find under: pitch
The theoretical forward distance a propeller would advance in one revolution without slip.
In practice
Topic references & further reading ↗Pitch is a geometric specification, not a promise of the boat’s distance travelled per revolution.
Engines & propulsion# Link to term
Propeller slip
Also find under: slip
The difference between theoretical pitch-based advance and actual advance, expressed under a chosen calculation.
In practice
Topic references & further reading ↗Slip is not the same phenomenon as cavitation; avoid diagnosing one solely from the other’s name.
Rigging & deck hardware# Link to term
Purchase
Also find under: mechanical advantage
An arrangement of lines and blocks that provides mechanical advantage.
In practice
Topic references & further reading ↗A nominal purchase ratio does not account for all friction or determine every component’s load.
Safety & communications# Link to term
PWC
Also find under: personal watercraft jet ski jetski
Personal watercraft: a compact powered craft generally ridden on, rather than within, a conventional hull cockpit.
In practice
Topic references & further reading ↗Jet Ski is a Kawasaki brand name, while PWC is the broader category used across brands.
Electronics & networks# Link to term
Radar
A system that uses radio-wave transmissions and their returns to detect targets and measure their relative position.
In practice
Topic references & further reading ↗Its display needs interpretation; it does not make every small object or hazard visible.
Sails & sailing# Link to term
Reefing
Also find under: reef
Reducing the sail area set, using the arrangement designed for that sail and rig.
In practice
Topic references & further reading ↗Ask the sailmaker and installer to describe the compatible reefing system rather than assuming all sails use the same method.
Rigging & deck hardware# Link to term
Rope clutch
Also find under: clutch
A device designed to hold a line under load and release it in a controlled arrangement.
In practice
Topic references & further reading ↗Confirm both the rope construction and diameter range with the clutch maker.
Navigation & charts# Link to term
Route
An ordered series of navigation legs or waypoints.
In practice
Topic references & further reading ↗An automatically proposed route still requires appropriate checking against current information and the vessel.
Engines & propulsion# Link to term
RPM
Also find under: revolutions per minute
Revolutions per minute, a measure of rotational speed.
In practice
Topic references & further reading ↗Engine rpm and propeller rpm differ where a reduction gear is used.
Rigging & deck hardware# Link to term
Running rigging
The adjustable lines and associated arrangements used to control sails and spars.
In practice
Topic references & further reading ↗Name each line’s function when requesting a replacement rather than ordering by colour alone.
Engines & propulsion# Link to term
Saildrive
A propulsion arrangement with a drive leg passing through the hull, commonly coupled to an inboard engine.
In practice
Topic references & further reading ↗Its seals, installation and servicing are distinct from a conventional shaft arrangement.
Weather, tides & anchoring# Link to term
Scope
Also find under: anchor scope
In anchoring, the ratio of rode deployed to the vertical distance from its attachment point to the seabed.
In practice
Topic references & further reading ↗State the reference height and tidal allowance when discussing scope; this is not a universal deployment recommendation.
Weather, tides & anchoring# Link to term
Sea waves
Also find under: wind waves seas
Waves generated by winds acting locally over the water.
In practice
Topic references & further reading ↗A forecast may report sea waves separately from swell; read both and their combined implications.
Engines & propulsion# Link to term
Shaft drive
An arrangement transmitting engine power through a shaft to a propeller outside the hull.
In practice
Topic references & further reading ↗A repower assessment includes alignment, supports and the existing drive arrangement, not just the engine footprint.
Rigging & deck hardware# Link to term
Sheave
The grooved rotating wheel within a block or similar line-handling fitting.
In practice
Topic references & further reading ↗A replacement sheave needs the correct dimensions, bearing arrangement and line compatibility.
Sails & sailing# Link to term
Sheet
Also find under: sail sheet
A line used to control a sail’s angle or trim.
In practice
Topic references & further reading ↗A sheet is a control line, not the sailcloth. Name the sail when ordering one.
Rigging & deck hardware# Link to term
Shroud
A rigging member providing lateral support to a mast.
In practice
Topic references & further reading ↗Wire size alone does not identify the complete shroud assembly or terminal compatibility.
Fishing & sonar# Link to term
Side-scanning sonar
Also find under: side imaging sidescan
Sonar presenting returns from areas to the sides of the vessel using a suitable system.
In practice
Topic references & further reading ↗Ask which transducer, module and display combination produces the demonstrated view.
Weather, tides & anchoring# Link to term
Significant wave height
Also find under: Hs combined sea and swell
A statistical wave-height measure approximately representing the average height of the highest third of waves.
In practice
Topic references & further reading ↗It is not the maximum individual wave; larger waves can occur.
Weather, tides & anchoring# Link to term
Snubber
Also find under: anchor snubber
An elastic line or arrangement used to soften loads, commonly in an anchoring setup.
In practice
Topic references & further reading ↗Its length, material and attachment need to suit the actual arrangement; a definition is not a sizing instruction.
Fishing & sonar# Link to term
Sonar
Also find under: sounder fishfinder
A system using sound transmitted through water and returning echoes to detect or measure underwater features.
In practice
Topic references & further reading ↗A display image represents processed echoes, not an underwater photograph or confirmed species identification.
Navigation & charts# Link to term
Speed over ground
Also find under: SOG
The rate of movement relative to the Earth’s surface.
In practice
Topic references & further reading ↗Current can make this differ from speed through the water without either sensor being wrong.
Navigation & charts# Link to term
Speed through water
Also find under: STW boat speed
The vessel’s speed relative to the surrounding water.
In practice
Topic references & further reading ↗Compare the sensor type and calibration before using it alongside ground speed.
Rigging & deck hardware# Link to term
Splice
Also find under: eye splice
A rope joint or termination made by interweaving or reconstructing its strands or braid.
In practice
Topic references & further reading ↗A suitable splice depends on rope construction and the maker’s procedure, not only its diameter.
Weather, tides & anchoring# Link to term
Spring tide
A tide occurring in the part of the cycle generally associated with larger tidal ranges.
In practice
Topic references & further reading ↗The name is related to the tidal cycle, not the season of spring.
Rigging & deck hardware# Link to term
Standing rigging
The stays and shrouds that support a mast in its working position.
In practice
Topic references & further reading ↗A standing-rigging inspection is a different scope from replacing worn sail-control ropes.
Boat anatomy & directions# Link to term
Starboard
Also find under: starboard side
The vessel’s right side when facing towards its bow.
In practice
Topic references & further reading ↗Specify starboard or port when sending installation photographs to a supplier.
Rigging & deck hardware# Link to term
Stay
A rigging member supporting a mast, commonly in a fore-and-aft direction.
In practice
Topic references & further reading ↗Specify forestay or backstay and the actual end fittings when discussing replacement parts.
Boat anatomy & directions# Link to term
Stern
Also find under: aft end
The after end of a vessel.
In practice
Topic references & further reading ↗A stern fitting may be on a transom or another part of the aft structure.
Weather, tides & anchoring# Link to term
Swell
Waves that have travelled beyond their generating wind area, or persist after that wind has eased.
In practice
Topic references & further reading ↗Calm local wind does not establish an absence of swell.
Sails & sailing# Link to term
Tack corner
Also find under: sail tack
The corner where the luff and foot meet on a conventional triangular sail.
In practice
Topic references & further reading ↗Tack also describes a sailing manoeuvre or which side receives the wind; specify the intended meaning.
Sails & sailing# Link to term
Tacking
Also find under: tack
Changing tack by turning the bow through the direction from which the wind comes.
In practice
Topic references & further reading ↗This term names the manoeuvre; practical training covers its execution for the particular boat.
Fishing & sonar# Link to term
Target separation
The ability of a sonar system to distinguish nearby echo-producing objects as separate returns.
In practice
Topic references & further reading ↗A demonstration should reflect the task and setup you care about, not just a favourable promotional image.
Fishing & sonar# Link to term
Terminal tackle
The hooks, sinkers, swivels, lures and other components at the fishing end of a line.
In practice
Topic references & further reading ↗Describe the fishing method and target when discussing a tackle arrangement with a specialist.
Electronics & networks# Link to term
Terminator
Also find under: network terminator
A component used to provide the specified electrical termination at a network end.
In practice
Topic references & further reading ↗A network end and an unused branch connector are not necessarily the same thing.
Weather, tides & anchoring# Link to term
Tidal range
The difference in water level between a high tide and a low tide under the stated comparison.
In practice
Topic references & further reading ↗A tidal range is not the same as the depth available at a specific moment.
Engines & propulsion# Link to term
Torque
Also find under: Nm
Turning effect of a force, commonly expressed in newton metres for engine output.
In practice
Topic references & further reading ↗Read torque together with engine speed and the rating basis rather than comparing peak figures alone.
Fishing & sonar# Link to term
Transducer
A device converting one form of energy to another; sonar transducers transmit sound and receive returning echoes.
In practice
Topic references & further reading ↗Specify the exact model and its display or module compatibility when comparing a fishfinder package.
Boat anatomy & directions# Link to term
Transom
The structure forming the stern face of many boats.
In practice
Topic references & further reading ↗An outboard or transducer installation requires the actual transom arrangement, not just the boat length.
Fishing & sonar# Link to term
Trolling
Also find under: fishing trolling
Fishing by drawing bait or lures through the water from a moving vessel.
In practice
Topic references & further reading ↗Do not confuse fishing by trolling with a transmission’s trolling-valve function or a trolling motor product category.
Weather, tides & anchoring# Link to term
True wind
Also find under: TWS TWA
Wind relative to a stated reference frame after accounting for the effect of vessel motion.
In practice
Topic references & further reading ↗Marine instruments may use water- or ground-referenced calculations; check the source before comparing values.
Navigation & charts# Link to term
Under-keel clearance
Also find under: UKC
The vertical separation between the lowest relevant part of a vessel and the seabed.
In practice
Topic references & further reading ↗A simple chart-depth subtraction omits factors such as tide, motion and uncertainty.
Engines & propulsion# Link to term
Ventilation
Also find under: propeller ventilation
In propulsion, air or exhaust gas entering the water flow at the propeller.
In practice
Topic references & further reading ↗Describe when the symptom occurs and have the installation assessed instead of assuming cavitation.
Safety & communications# Link to term
VHF
Also find under: very high frequency marine radio
Very High Frequency: a radio-frequency band used for marine communications.
In practice
Topic references & further reading ↗A marine VHF set and a mobile phone use different systems; one label does not establish coverage for a trip.
Safety & communications# Link to term
Waterjet
Also find under: jet drive
A propulsion system that accelerates water through a pump and nozzle to generate thrust.
In practice
Topic references & further reading ↗A waterjet craft’s handling and maintenance differ from a propeller-driven installation; use model-specific instruction.
Boat anatomy & directions# Link to term
Waterline
The line where the hull meets the water surface in a particular loading condition.
In practice
Topic references & further reading ↗Added load can change the actual waterline from the design or painted mark.
Weather, tides & anchoring# Link to term
Wave period
Also find under: swell period
The time between successive wave crests passing a point, under the particular period measure used.
In practice
Topic references & further reading ↗Check whether a forecast means peak or another period measure before comparing numbers.
Navigation & charts# Link to term
Waypoint
A stored geographical position used as a reference in navigation.
In practice
Topic references & further reading ↗A saved waypoint records a position; it does not establish that reaching it is safe or permitted.
Rigging & deck hardware# Link to term
Winch
A rotating-drum device that assists hauling or controlling a loaded line.
In practice
Topic references & further reading ↗A winch’s model designation is not a universal statement of permitted line load.
Rigging & deck hardware# Link to term
Working load limit
Also find under: WLL maximum working load MWL
The manufacturer’s permitted working load under its stated conditions and application.
In practice
Topic references & further reading ↗Do not use a breaking-load figure as the normal working allowance for a component.
How to use this reference
Definitions explain terminology. The practical notes are editorial examples of how a term can affect a purchase or a conversation. Topic pages link to specialist and official further reading. These sources do not endorse MarineBrands, and terminology can vary between standards, manufacturers and contexts.
Use the current manufacturer documentation for a specific installation and the responsible authority for operating, safety or fishing requirements. A definition is not a substitute for training, a navigation assessment or a current rule.
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