Nautical Terminology

  • Ahead - going forwards
  • Aft - when you're moving backwards, you're 'going aft' 
  • Aground - when your vessel is in contact with the seabed
  • Astern - going backwards
  • Beam - the width of vessel (usually at widest point)
  • Cavitation - Extreme reduction in pressure on the back side of the blades (often confused with ventilation)
  • Draft - how deep the water needs to be for the vessel to float
  • Ventilation - result of exhaust gases being pulled into propellor blades causing the blades to lose grip, RPM to increase and speed to reduce.
  • Wake - turbulence behind a vessel
  • Wash - the waves a vessel creates as it moves through the water
  • Way - Progress through the water i.e. making way


The term "current" describes the motion of the water. Oceanic currents are driven by several factors. One is the rise and fall of the tides. Tides create a current in the oceans, near the shore, and in bays and estuaries along the coast. These are called "tidal currents." Tidal currents are the only type of currents that change in a very regular pattern and can be predicted for future dates.

A second factor that drives ocean currents is wind. Winds drive currents that are at or near the ocean's surface. These currents are generally measured in meters per second or in knots (1 knot = 1.85 kilometers per hour or 1.15 miles per hour). Winds drive currents near coastal areas on a localised scale and in the open ocean on a global scale.

A third factor that drives currents is thermohaline circulation - a process driven by density differences in water due to temperature (thermo) and salinity (haline) in different parts of the ocean. Currents driven by thermohaline circulation occur at both deep and shallow ocean levels and move much slower than tidal or surface currents. - Ref Author: National Oceanic and Atmospheric Administration


A knot is one nautical mile per hour (1 knot = 1.15 miles per hour). The term knot dates from the 17th century, when sailors measured the speed of their ship by using a device called a "common log." This device was a coil of rope with uniformly spaced knots, attached to a piece of wood shaped like a slice of pie. The piece of wood was lowered from the back of the ship and allowed to float behind it. The line was allowed to play out freely from the coil as the piece of wood fell behind the ship for a specific amount of time. When the specified time had passed, the line was pulled in and the number of knots on the rope between the ship and the wood were counted. The speed of the ship was said to be the number of knots counted (Bowditch, 1984). - Ref Author: National Oceanic and Atmospheric Administration


a leeward vessel is downwind

Nautical Mile

A nautical mile is based on the circumference of the earth, and is equal to one minute of latitude. It is slightly more than a statute (land measured) mile (1 nautical mile = 1.1508 statute miles). Nautical miles are used for charting and navigating.

Ref Author: National Oceanic and Atmospheric Administration

Port & Starboard

When looking forward, toward the bow of a ship, port and starboard refer to the left and right sides, respectively.

In the early days of boating, before ships had rudders on their centerlines, boats were controlled using a steering oar. Most sailors were right handed, so the steering oar was placed over or through the right side of the stern. Sailors began calling the right side the steering side, which soon became "starboard" by combining two Old English words: stéor (meaning "steer") and bord (meaning "the side of a boat").

As the size of boats grew, so did the steering oar, making it much easier to tie a boat up to a dock on the side opposite the oar. This side became known as larboard, or "the loading side." Over time, larboard—too easily confused with starboard—was replaced with port. After all, this was the side that faced the port, allowing supplies to be ported aboard by porters. - Ref Author: National Oceanic and Atmospheric Administration


Tides are one of the most reliable phenomena in the world. As the sun rises in the east and the stars come out at night, we are confident that the ocean waters will regularly rise and fall along our shores.

Tides are very long-period waves that move through the oceans in response to the forces exerted by the moon and sun. Tides originate in the oceans and progress toward the coastlines where they appear as the regular rise and fall of the sea surface.

When the highest part, or crest, of the wave reaches a particular location, high tide occurs; low tide corresponds to the lowest part of the wave, or its trough. The difference in height between the high tide and the low tide is called the tidal range. - Ref Author: National Oceanic and Atmospheric Administration

Tidal Range

The difference in height between the high tide and the low tide is called the tidal range.


Windward means "upwind," or the direction from which the wind is blowing. A windward vessel refers to one that is upwind of another vessel

Parts of a vessel:

  • Bilge - the compartment/s at the bottom of the hull
  • Bow - the front of the vessel
  • Cabin - an enclosed room
  • Console - Where the vessel controls are located i.e. steering, switches, throttle etc
  • Cleat - device for securing a rope
  • Cuddy - a small cabin
  • Freeboard - distance from the waterline to the gunwale 
  • Gunwale - upper most edge  of the vessels hull 
  • Head - Vessel's toilet
  • HIN - Hull Identification Number
  • Hull - the shell / framework of a vessel
  • Sponson - part of a craft at or below the waterline that extends from the hull to aid stabilty, it also increases floatation and lift when underway
  • Stern - rear of the vessel
  • Transom - the vertical or near vertical wall at the stern of the vessel, (if you have an outboard on a powerboat, this is where it will be attached)
  • Windlass - a mechanical winch mechanism (i.e. anchor windlass)


  • Bowline - a type of knot with a strong loop
  • Drogue - a deliver to slow a boat down or stabilise it in heavy weather (also known as a sea anchor)
  • EPIRB - Electronic Position Indicating Radio Beacon
  • Fender - a flexible bumper
  • Flare - pyrotechnic signally device
  • Painter - a rope attached to the bow of a vessel
  • PFD - Personal Floatation Device
  • PLB - Personal Locator Beacon
  • Radar - RAdio Detection And Ranging
  • Spring Line - a mooring line that goes from the bow of the vessel to a cleat on the pontoon adjacent to the stern or vice versa from the stern of the vessel to a cleat adjacent to the bow. 
  • VHF - Very High Frequency
  • Warp - a rope used to attach to a fixed object