coastalnavigation.com

Glossary of Nautical
and Navigational Terms

NOTE: This Glossary covers terms and other information beyond that of Sail Canada's Basic Coastal Navigation Standard.

A

 Alpha "I have a diver down." Morse code
• – (di-dah)

Abaft: a position on a boat further aft than a specified position.
Abeam: across the fore-and-aft line of a boat.
Adrift: an object without mooring; a boat with no rudder or means of propulsion.
Advanced LOP: an LOP which has been moved parallel to itself along a course line.
Aft: near or toward the stern of a boat.
Aground: resting on the bottom.
Ahead: the direction of an object beyond the bow of a boat; the passage of a vessel through the water in the direction in which her bows are pointing; see also Dead ahead.
Aid: an aid to navigation; a device or structure designed to assist in the determination of the position of a boat, to facilitate a safe course, and to warn of dangers or obstructions.
Aloft: above the deck.
Alternating light: a light that changes its features of colour, sequence or phase.
Amidships: at, near or toward the middle of a boat.
Angle of cut: a small angle between two bearings or LOPs on a chart.
Angular distance: the angle between two bearings or directions; the distance between two points on an arc expressed in degrees.
Annual drift: the yearly change in the geographical position of the magnetic pole, printed on the arrow of the compass rose; also called annual change.
Approach chart: a chart of large scale, for example 1:8 000, often showing harbour entrances.
Arc: part of a curved line, usually a semi-circle or the circumference of a circle.
Ashore: on shore, land or ground.
Astern: the reciprocal direction of dead ahead; of a vessel moving backwards.
Athwartships: across the boat, usually across the beam.
Aweigh: of an anchor, broken out or just off the bottom.

B

 Bravo "Carrying dangerous goods." – • • • (dah-di-di-dit)

Back bearing: the reciprocal reading of a bearing dead ahead, often taken on a range or on leading lights.
Back range: a range made by lining up objects astern, the reciprocal of which provides a precise course ahead, usually in channels.
Beacon: a mark over a shoal or on land to aid navigators.
Beam tide: a tide setting at 90° to the heading or course of a boat; also beam wind.
Bear: to turn away from, to turn leeward, to bear away from the wind; .
Bearing: the direction of one object or point from another expressed in degrees.
Bifurcation buoy: a lateral-system marker that divides a channel into two, with the preferred channel identified by the major colour (green or red).
Binnacle: the stand on which a compass is mounted.
Boat's compass: see Steering compass.
Box the compass: to name the thirty-two points of the compass clockwise from north.
Buoy: a floating or fixed aid to navigation; often shaped as a spar, pillar, or cylinder.
Buoyage system: the system in which buoys are classified according to shape, colour, number and function.

C

 Charlie "Yes." – • – • (dah-di-dah-dit)

Canadian buoyage system: Canada belongs to Region B of the IALA maritime buoyage system.
Canadian Hydrographic Service (CHS): of the Department of Fisheries and Oceans; produces charts of Canada's coastline and inland waterways. http://www.chs-shc.dfo-mpo.gc.ca/
Canadian Power and Sail Squadrons (CPSA): a volunteer organization that specializes in boating education. http://www.cps-ecp.ca/
Canadian Yachting Association (CYA): the national governing body in Canada for yachting, dinghy sailing, windsurfing, cruising and racing on small sailboats and keelboats. http://sailing.ca/
Cardinal points: the major points of the compass, namely east, south, west and north.
Cardinal system: a system of buoys that indicate the direction of safe water by: 1) colour coding 2) top-marks 3) light sequence, and 4) name.
Cartography: the art and science of producing maps and nautical charts.
Chandlery: items of nautical gear to fit out a vessel; a store where such items are sold.
Channel: the deepest part of any body of water in streams, rivers, bays and straits.
Chart: a flat and scaled representation of a part of the earth's sea surface.
Circles of uncertainty: progressively larger circles along a DR course showing possible positional errors of the boat.
Chart No. 1or Chart 1: sub-titled Symbols Abbreviations and Terms Used on Nautical Charts; a publication of the CHS.
Chart datum: a water level to which depths and drying heights are referenced.
Chart symbol: the symbols, graphic, lettered or numbered, in Chart 1 to indicate an object or characteristic.
Close aboard: nearby.
Coast Guard, Canadian (CCG): of the Department of Fisheries and Oceans; ensures the safe and environmentally responsible use of Canada's waters, provides rescue services and maintains Canada's navigational aids. http://www.ccg-gcc.gc.ca/
Coast Pilots: a US reference of navigational aids and other information for coastal navigation.
Coastal current: a current that follows a coastline seaward of the breaking surf.
Coastal navigation: the art of navigating using visual aids as references and water depths from charts; see also Piloting.
Cocked hat: a triangle given by three LOPs or bearings that do not cross at the same point.
Colregs: Collision Regulations, a contraction of International Regulations for Preventing Collisions at Sea, 1972, with Canadian Modifications , also called the "rules of the road"; an international convention for safety at sea that governs the behaviour of vessels.
Compass: a magnetic device that provides a horizontal reference direction.
Compass adjustment: the process of minimizing undesired magnetic affects on a compass.
Compass bearing: the bearing taken by a boat's compass relative to compass north.
Compass card: in a compass, the rotating disk marked with directional graduations.
Compass course: the course followed by the helmsperson using the boat's steering compass.
Compass direction: the horizontal direction in degrees from compass north.
Compass heading: the heading of a boat relative to compass north.
Compass points: the thirty-two points of the compass, at intervals of 11 ¼° apart.
Compass rose: an imprint on a nautical chart of two concentric circles with 360° graduated clockwise; the outer circle depicts true north degrees and the inner magnetic, with annual variation.
Composite group flashing: on a lighted aid to navigation, a repeated sequence of two or more grouped flashes separated by a period of darkness.
Conn: to control, steer or manoeuvre a boat.
Contour line: a line shown on nautical charts connecting points of equal depths above or below datum; see Fathom line and Line of soundings.
Co-ordinates: the descriptor of a boat's position using latitude and longitude.
Correcting: the process of converting compass or magnetic direction to true direction.
Course: the direction a boat travels, in degrees from north clockwise through 360°.
Course made good (CMG): the course over the ground from departure to arrival.
Course of advance: see Track.
Course over ground: see Course made good or Track.
Course to steer (CTS): the course followed to compensate for the calculated effects of current.
Cross bearing: the point where two bearings taken from a boat cut each other.
Current: the horizontal movement of water, tidal or non-tidal.
Current direction: the direction toward which the water is flowing, see also Set.
Current rose: a diagram of arrows whose length represent tidal current strength and direction.
CYA Coastal Navigation Standard: the standard of theoretical competence required to navigate a boat safely in coastal and inland waters.

D

 Delta "Keep clear." – • • (dah-di-dit)

Danger angle: an angle between two points indicating the limit of a safe approach around an off-lying danger; a line on a chart representing the danger zone; also danger bearing.
Danger line: a line drawn on a chart to indicate the limits of safe navigation.
Datum: the level below which the water seldom falls.
Daybeacon: an unlighted beacon with distinctive colour and shape; also called daymark.
Dead ahead: a bearing 000° relative to the bow.
Dead astern: a bearing 180° relative to the bow.
Dead reckoning: the determination of a boat's position based only on distance, time and speed, and a known departure point.
Degree: a unit of measure on a circle equal to 1/360th of the circle.
Departure point: the position of a fix representing the start of a DR course.
Depth curve: see Contour line.
Depth sounder: an electronic device for measuring the depth of the sea bottom beneath a boat.
Depths: units of soundings in feet, metres or fathoms.
Deviation table: a table of the differences between the boat's compass and magnetic readings.
Deviation: the difference in degrees between magnetic north and compass north, caused by magnetic influences on a boat.
Directional light: a light illuminating a sector of narrow angle to show a safe channel .
Diurnal: a period or cycle of one day; a diurnal tide rises and falls every twenty-four hours.
Dividers: a plotting tool for measuring or transcribing distance on a nautical chart.
Draft: the depth below a boat's waterline.
Drift: the speed of current; the distance a boat is moved by current.
Drying heights: heights above chart datum that are periodically covered and uncovered.
Duration of flood, ebb: the time interval during which the tidal current is flooding or ebbing.

E

 Echo "I am altering course to starboard." • (dit)

Ebb: tidal current flowing to the sea.
Electronic chart: a chart displayed on a video terminal, usually in colour.
Electronic compass: a compass that senses the earth's magnetic field electronically.
Electronic navigation: navigation by means of such electronic equipment as depth sounders, electronic compasses, radar, and satellite navigation systems.
Electronic Position Indicating Radio Beacon (EPIRB): a small portable radio beacon used by offshore boaters and aircraft in distress that transmits radio signals to aid search and rescue efforts.
Elevations: heights of objects above chart or tidal datum.
Equal-interval light: see Isophase.
Equator: the great circle equidistant from the poles that encompasses the earth and is perpendicular to the axis of the poles; divides the earth into northern and southern hemispheres and represents the line from which parallels of latitude are measured.
Estimated position (EP): a DR position upgraded by additional information.
Estimated Time of Arrival (ETA): a forecast time of reaching a destination.
Estimated Time of Departure (ETD): a forecast time of leaving a departure point.

F

 Foxtrot "I am disabled." • • – • (di-di-dah-dit)

Fair tide: a tidal current setting so as to increase the speed of a vessel.
Fairway buoy: a buoy that marks the middle of a channel or a series of channel markers.
Fairway: the main channel of a body of water with a series of navigational markers.
Falling tide: the tidal phase when the water level drops during its ebb.
Fathom line: a contour line of equal depth soundings.
Fathom: a unit of depth measurement of six feet.
Fix: to determine the position of a boat by any means, electronic or visual; a position of a boat determined by bearings, visual or electronic.
Fixed light: a navigational light that emits a steady illumination.
Flashing: of a navigational light where the duration of illumination is shorter than that of darkness.
Flood current: the movement of a tidal current toward the shore, inwards in an estuary, upstream, or to the head of a lake.
Flood: the flow of a tidal stream as it rises.
Fluxgate compass: an electronic compass that measures the earth's lines of magnetic influence and indicates direction.
Fog signals: prescribed warning signals under the Colregs for use in low visibility.
Fore-and-aft: parallel to the line between stem and stern; a line at right angles to Athwartships.

G

 Golf "I require a pilot." – – • (dah-dah-dit)

Global Positioning System (GPS): a US system of satellite navigation.
Gnomonic projection: a projection in which great circle lines are projected as straight lines; other distortions occur as meridians converge to the pole and parallels curve; used in small scale (ocean) charts as great circle may be preferred to rhumb line courses.
Great circle: a circle on a sphere where the circle's plane passes through the centre of the sphere; the line of shortest distance between two points on the earth's surface.
Great-circle chart: a chart on which a great circle appears as a straight line, especially on a gnomonic chart.
Greenwich mean time (GMT): time at the Greenwich, England; replaced by Universal co-ordinated time in 1986 as the standard to which the world's time zones are referenced; see also Universal time (UTC) and Zulu time.
Greenwich meridian: the prime meridian at longitude 000° which passes through the Greenwich observatory.
Group-flashing: a sequence of flashes separated by a period of darkness.

H

 Hotel "I have a pilot on board." • • • • (di-di-di-dit)

Hand-held compass: a portable compass that can be removed from the influences of a boat's magnetism; also called a hand-bearing compass.
Harbour: an anchorage, constructed or natural, with jetties, breakwaters and docking facilities.
Heading: the direction in which a boat is pointed.
Height of tide: the vertical distance from tidal datum to the water's surface.
Helm: the tiller or wheel; also the person in command of a boat.
High water: maximum height above tidal datum reached by a rising tide.
Higher High Water: the tidal water level reached during high water, large tide above tidal datum.
Hour diagram: a vector diagram used to determine set, drift or course to steer over one hour based on speed, time and distance.

I

 India "I am altering my course to port." • • (di-dit)

International Association of Lighthouse Authorities (IALA): a United Nations body of maritime nations that regulates the world's two main buoyage systems; http://www.iala-aism.org/uk/
International Hydrographic Organization (IHO): an intergovernmental organization dedicated to safety in navigation and the protection of the marine environment. http://www.iho.shom.fr/
International nautical mile: 1,852 metres, or 6,076.12 feet; also called sea mile.
Inter-cardinal points: the points of the compass card in between north, east, south and west known as northeast (NE), southeast (SE), southwest (SW) and northwest (NW).
Isolated danger buoy: a navigational aid that marks a danger with safe water all around it; it is black with a red band and has two black ball top marks.
Isophase: a light phase where the period of darkness equals the time of light.

J

 Juliett "Keep well clear. On fire." • – – – (di-dah-dah-dah)

Jetty: a structure that projects from the shore to which boats can be tied.
Junction buoy: see Bifurcation buoy and Daybeacon.

K

 Kilo "I wish to communicate with you." – • – (dah-di-dah)

Kelp: a tuberous seaweed that lies at the water's surface and poses a hazard to navigation.
Kilometre: 1,000 metres or about 0.54 of a nautical mile.
Knot: a measure of speed equal to one nautical mile per hour.
Knotmeter: a device, usually electronic, for measuring a boat's speed through the water.

L

 Lima "Stop your vessel instantly." • – • • (di-dah-di-dit)

Large scale: ratio between the linear dimensions on a chart and the true dimensions of the area; a large scale chart, for example 1:8 000, may cover a small area such as a harbour.
Lateral mark or buoy: a navigational aid, usually floating, that indicates the side of a channel.
Lateral system: a Canadian aids to navigation system that identifies channels and underwater dangers using buoys or daybeacons and the colours red, green, black and white.
Latitude: a line or small circle parallel to the equator and running east-west; the angular distance in degrees from the centre of the earth to a parallel north or south of the equator; see also Parallels.
Leading lights: two or more lights in line showing a safe channel; see also Range.
Leading line: a solid line on a chart indicating safe water.
Leeward: the direction away from the wind; the opposite direction from which the wind blows.
Leeway: the sideways slippage of a boat due to wind and waves; the angle seen in the wake of a boat dead astern to the wake stream.
Lights List: a contraction of List of Lights, Buoys and Fog Signals issued by the Coast Guard.
Light sector: a wide beam from light stations; the limits and bearings are indicated on charts.
Lighthouse: an older term for an inhabited light station; see also Light station.
Light station: a tower on the coastline that exhibits lights and fog signals, usually unattended.
Line of position: see LOP.
List of Lights, Buoys and Fog Signals: a publication of Fisheries and Oceans Canada that provides latitude and longitude, flashing characteristics and descriptions of aids to navigation.
Local magnetic disturbance: an alteration to the local variation.
Log: a skipper's on-board record of courses plotted, fixes, and bearings and other notable events; a mechanical device for tallying miles a boat has traveled through the water.
LOP: a plotted line indicating the direction of an object from an observer and on which the boat is located.
Longitude: the angular distance east or west of the prime meridian that runs through Greenwich.
LORAN-C: a contraction of LOng RAnge Navigation system; a radio-based electronic navigation system.
Low water: the level reached by a falling tide.
Lower low water: the lowest level reached during low water, large tide.
Lubber's line: a reference mark on a boat's compass aligned fore-and-aft indicating the heading of a boat.

M

 Mike "My vessel is stopped." – – (dah-dah)

Magnetic bearing: a bearing from a hand-held compass with magnetic north as its reference.
Magnetic compass: a direction-finding device with a free-spinning compass card that responds to the earth's magnetic field.
Magnetic course: the course of a boat with reference to magnetic north.
Magnetic north: the direction to which the compass needle points if no deviation is present; its focal point is 700 nm south of the geographic north pole in the direction of the prairie provinces.
Marker: same as mark; see Buoy.
Mercator: a 16th-century Flemish cartographer-businessman; a chart projection with lines of latitude and longitude at right angles to each other, created by Gerhard Mercator.
Meridian: a line of longitude that runs from the north to the south pole and cuts the equator and parallels of latitude at right angles.
Mid-channel buoy: a marker which designates the middle of a channel and can be passed on either side; same as Fairway buoy.
Minute: one sixtieth of a degree; on a Mercator chart a minute of latitude is equal to one nautical mile.

N

 November "No." – • (dah-dit)

Nautical chart: a flat representation of a portion of the earth's spherical surface, usually on paper or electronic.
Nautical mile: a sea mile; 1,852 metres or 6,076.12 feet; the length of one minute of a great circle, and the length of one minute of latitude.
Navigate: to guide a boat safely from one place to another by reference to nautical charts and a compass, with or without electronic means of assistance.
Neap tides: smaller tides that occur when the sun , moon and earth are not in line; the range is less and tidal streams run less strongly.
North pole: the northernmost point of the earth around which the world rotates.
Notices to Mariners (NOTAMS): information published by Canadian and US Coast Guards and other agencies to update charts and navigational publications in each country.

O

 Oscar "Person overboard." – – – (dah-dah-dah)

Obscured: the part of the light sector where a sector light cannot be seen.
Observed position: a boat's position where two LOPs and a bearing intersect.
Obstruction: a danger to navigation, sometimes marked.
Occulting: a light sequence in which the duration of illumination is longer than that of darkness.
Ocean currents: the horizontal movement of water in the oceans.
Over ground: over the seabed, as in courses, speed and distances made good; see also Track.

P

 Papa "Come aboard,
vessel is about to sail."		 • – – • (di-dah-dah-dit)

Parallel rulers: a navigation tool used to transfer directions on a chart.
Parallel: a line of latitude parallel to the equator; a small circle connecting all places on earth of the same latitude.
Period: the completion time for a light sequence, whether rhythmic, alternating or group flashing.
Phase: the duration of a light or its eclipse.
Pilot: a British publication providing details about currents, dangers, obstructions, tidal currents, harbour regulations; in the USA these publications are Coast Pilots and in Canada Sailing Directions.
Piloting: the act of navigating using visual aids as references and water depths from charts; same as coastal navigation.
Planning chart: a small scale ocean chart used in cruise planning.
Plot: to lay off or draw a boat's position or planned course on a nautical chart, usually based on time, distance, speed and point of departure.
Polyconic: a type of chart projection in which the earth's surface is projected onto a series of cones, one for each parallel of latitude.
Port: the left side of the boat when facing forward.
Port buoy: the green buoy found to the left when proceeding upstream, with the tidal flood current, to the head of a lake, to higher water in a canal system, or clockwise around North America; red-right-returning, (green going) applies in Region B of the IALA.
Position: a boat's latitude and longitude that describes its location on the earth's surface.
Position finding or position determination: the navigational process of estimating a boat's position.
Position line: a line of position or LOP that indicates a boat's location on the line.
Predicted tides: the tides listed in the tide tables.
Prime meridian: the meridian that runs north and south through Greenwich, England.
Projection: in cartography, a mapping of a geometric figure from one plane to another.
Protractor: an instrument for measuring angles.

Q

 Quebec "Await clearance to disembark." – – • – (dah-dah-di-dah)

Quadrant: one-quarter of a circle; an arc of 90°.
Quick flashing: a white or coloured navigational light that flashes 50 or 60 times per minute.

R

 Romeo • – • (di-dah-dit)

Racon: a radio beacon that reflects a radar signal from a vessel and transmits an identifying code.
Radar reflector: a passive device that reflects another boat's radar signal.
Radar: a contraction of RAdio Detection And Ranging: an electronic instrument that emits and detects reflected radio signals from objects and illuminates them on a display.
Radio Aids to Navigation: a list of aids that provide radio frequency information such as location, Morse code identifier, and the range from the electronic transmitter.
Radio beacon: see Racon.
Radio direction fnder: a direction-seeking device that uses radio waves from navigational stations
Range: a line or series of objects that indicate a safe channel for boats to follow .
Range of tide: the difference in height between high and low tides.
Rate: the speed of a current in knots; see also Drift.
Reciprocal course or bearing: a direction that differs by 180°.
Red-right-returning: the aide-memoire indicating safe water to the left of red starboard markers when traveling upstream, to the head of lakes, to a higher level in a canal system, and clockwise around North America.
Reference ports: ports for which tidal predictions are published.
Region A and Region B: regions of the world's maritime nations; in Region B red is kept to the navigator's right-hand side and green to the left when returning from sea or heading upstream; in Region A, the colours of red and green are reversed in position.
Relative bearing: a direction relative to a boat's bow, considered to be 000°.
Reversing current: a tidal current that flows alternately in the opposite directions.
Rhumb line: a line from two points on a chart that cuts all meridians at the same angle.
Rip current: a narrow and fast current, usually tidal.
Rise of the tide: the height a tide rises from datum to its high water datum.
Route: a selected course or path of travel based on DR planning.
Rules of the Road: see Colregs.
Running fix: a position determined by intersecting lines of position taken at different times.

S

 Sierra "Engine going astern." • • • (di-di-dit)

Safe water mark: see Fairway buoy.
Sailing Directions: official Canadian publications for use in navigation with detailed descriptions of waterways, tides, currents, weather, buoyage systems, signals, harbours, coasts and dangers and obstructions; see also Pilots (UK) and Coast Pilots (USA);
Sailing triangle: the vector diagram that depicts the effects of set and drift on a boat 's DR course.
Satellite navigation: position finding using radio transmissions from satellites; see GPS.
Scale: proportional representation of a large water and/or land area on a chart or map.
Sea mile: see Nautical mile.
Secondary channel: a navigable channel less used than the preferred channel.
Secondary ports: ports for which tidal time and height differences are published.
Second: one sixtieth of a minute in angular measurement of distance.
Sector light: a light emitting a wide beam, usually with sectors of different colours.
Semi-diurnal tide: one with two highs and two lows every 24 hours.
Shipping lane: a traffic lane or track for commercial traffic; on charts in magenta.
Shoal: a shallow area, often extending from a point of land.
Slack water: the period at the turn of the tide when the tidal current has stopped, or nearly so.
Small circle: a parallel of latitude whose plane does not pass through the centre of the earth.
Small scale: the ratio between the linear dimensions on a chart and the true dimensions of the area; a small scale chart such as the Gulf of St. Lawrence chart has a scale of about 1:500 000.
Soundings: estimates of water depths under a boat.
SOS: international distress signal; Morse "dah-dah-dah - di-di-dit - dah-dah-dah".
Spar: pole or pole-like structure used as an aid to navigation.
Special system of buoys: the third category of buoys within the Canadian aids to navigation system which are not primarily used for navigation purposes, and are either white or yellow.
Speed: the ratio of distance covered to the time taken, in knots.
Speed made good (SMG): the speed in knots over the sea bottom.
Speed through the water (STW): the speed that the boat will be traveling through the water regardless of the boat's speed over the sea bottom.
Spring tide: higher tides that occur when the moon and sun are in line; the range of tide is at its greatest and the tidal currents run strongest; compare to Neap tides.
Stand: the time period when the tide has stopped rising or falling.
Starboard: the right-hand side of the boat when facing forward.
Starboard buoy: the red buoy on the right side when proceeding upstream, with the tidal flood current, to the head of a lake, to higher water in a canal system, or clockwise around North America; red-right-returning, (green going) applies in Region B of the IALA Maritme Buoyage System.
Steering compass: the helms person's compass used to steer the boat.
Swinging ship: turning a boat through the points of the compass and noting magnetic headings compared to compass headings, the difference being deviation.

T

 Tango "Keep clear." – (dah)

Tidal current charts or Tidal atlas: current charts for large bodies of tidal water.
Tidal current: the horizontal movement of the water in response to tidal forces.
Tidal datum: same as Chart datum for tidal waters.
Tidal differences: the times and heights for high and low water at reference and secondary ports.
Tidal waters: the parts of oceans, coastal areas, and estuaries affected by tides.
Tide and Current Tables: the daily tables for one year with the predicted times of tides and heights, slack water, the maximums of currents, and their directions at identified points.
Tide: the vertical rise and fall of ocean waters in response to the gravitational forces of the moon, sun and the centrifugal force of a rotating earth.
Title block: text on a nautical chart that describes information for the area; includes the crest of the publishing agency, the IHO crest, regional identification, the main title, scale, projection, depths, elevations, datum and other references to Chart 1.
Top mark: the geometric shape fitted atop a buoy or beacon for identification purposes.
Track or track made good: the path followed by a boat over the sea bottom.
Traffic separation zone: one-way traffic lanes on charts, in magenta.
Transferred position line: see Advanced LOP.
Transit: see Range.
True bearing: a direction line relative to true north.
True course: a boat's course or heading relative to true north.
True north: north relative to the geographic north pole.
Turn of the tide: time when the tidal current changes direction; does not necessarily coincide with high or low water.

U

 Uniform "You are running into danger." • • – (di-di-dah)

Uncorrecting: adding or subtracting variation and deviation to a true reading of the compass to get the magnetic or the boat's compass reading; same as Converting.
Underway: a boat which is not made fast to shore, not at anchor and not aground.
Universal time: same as Universal Co-ordinated Time (UTC); the standard to which the world's time zones are referenced; replaced Greenwich mean time in 1986.
Unmanned light: an automated light, usually solar powered.
Upstream: in a river or tidal stream, the direction away from the ocean or against the current.
US buoyage system: the USA belongs to Region B within the IALA maritime buoyage system.

V

 Victor "I require assistance." • • • – (di-di-di-dah)

Variation: the difference in degrees between magnetic north and true north.
Vector: a plotted line representing both force and direction; in an hour diagram the current arrow represents its direction (set) and its length represents force (drift).
Vertical clearance: the height above datum to an overhead cable, bridge, etc., above higher high water large tide in Canada or, in the USA, above mean high water (MHW),.
Very quick flashing: the rapid flashing of a navigational light, 100 to 120 flashes per minute.
VHF radio: a ship-to-ship and ship-to-shore radio found on recreational and commercial boats; in the very high frequency range.
Visual range of light: the predicted range or distance at which a light can be seen.

W

 Whiskey "I require medical assistance." • – – (di-dah-dah)

Wake: the turbulence behind a boat caused by its passage; useful in establishing leeway.
Wash: the surging action of waves from a boat or natural causes.
Waterway: a navigable channel or canals in lakes, harbours, rivers,etc.
Waypoint: a reference point on a track; often determined in advance for passage planning.
Windward: the direction from which the wind blows; toward the wind; opposite is Leeward.

X

 X-ray "Stop. Watch for more signals." – • • – (dah-di-di-dah)

X-axis: the vertical axis in a co-ordinate or grid system; corresponds to meridians of longitude in the world's system of co-ordinates.

Y

 Yankee "I am dragging my anchor." – • – – (dah-di-dah-dah)

Y-axis: the horizontal axis in a co-ordinate or grid system; corresponds to parallels of latitude in the world's system of co-ordinates.
Yacht: a pleasure craft, for sailing or motoring, but not for commercial purposes; generally not small craft such as dinghies, row boats, etc.

Z

 Zulu "I require a tow." – – •• (dah-dah-di-dit)

Zulu: the time zone of the prime meridian at Greenwich, England; Tide and Current Tables display local standard time as the number of hours distant from Greenwich, or Zulu, time abbreviated as "Z", plus or minus the number of hours to determine UTC.