Glossary Archive

The ability of a person to maintain balance and move steadily on a vessel in motion, particularly in rough seas. Sealegs is a term deeply rooted in maritime culture, describing the adaptation process by which individuals become accustomed to the motion of a boat or ship at sea. When someone has "found their sealegs," it...

The coordinated efforts undertaken to locate and assist individuals in distress or imminent danger, typically at sea, and to bring them to safety.  Search and Rescue (SAR) is a critical operation in maritime environments, designed to respond to emergencies where individuals are lost, injured, or in peril. These operations are often carried out by specialised...

An emergency device that responds to radar signals by transmitting a series of pulses to help rescuers locate a vessel or liferaft in distress.  A Search and Rescue Transponder (SART) is an essential piece of safety equipment used in maritime emergencies to assist in locating vessels, liferafts, or individuals in distress. When activated, a SART...

A location where tidal information is derived by applying corrections to data from a nearby Standard Port.  A secondary port is a coastal location where tidal predictions are calculated by referencing a nearby standard port, which has a full set of tidal data. Since not all ports have their own dedicated tidal observations, secondary ports...

Substitute or repeater flags allow messages with duplicate characters to be signalled without requiring multiple sets of flags.

Occasionally a light may not be visible through 360 degrees, or it may shine different colours depending on where it is viewed from. In this instance the arcs or sectors of visibility and colours will be shown on the chart by dotted lines and a description of the sector such as 'obscured', 'W' (white light),...

A maritime safety message broadcast over radio to convey important but non-urgent navigational or weather-related information. Sécurité is a term used in maritime communications, particularly over VHF radio, to preface messages that concern the safety of navigation or provide important weather warnings. It is part of the Global Maritime Distress and Safety System (GMDSS) and...

A signalling system used to convey information at a distance by means of visual signals, typically using flags or lights. Semaphore is a traditional method of communication that has been used in maritime contexts for centuries. It involves the use of flags or other visual indicators, such as lights or mechanical arms, to send messages...

A semi-displacement hull combines the features of a planing vessel along with a displacement hull. The vessel will rise at the bow as she increases speed but will never fully reach the ‘plane’

Vertical movement of waves or swell against, for example, a harbour wall