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Nautical Know How
  • Our Courses

      All our courses are engaging, interactive and fun! Whether formal training or simply looking to brush up, we take online learning to the next level.

      • Sailing EssentialsFreeA free course great for anyone who spends time on the water.
      • Essential Navigation & SeamanshipRYA course for beginners. Learn charts, tides, pilotage, and core seamanship with simple practice tasks.
      • Day Skipper TheoryMost PopularRYA course for inshore skippers. Plan day passages using chartwork, tides, weather, and COLREGs.
      • Coastal Skipper / Yachtmaster® TheoryComing SoonRYA course for advanced navigation and passage planning. Work with secondary ports, tidal streams, and offshore weather.
      • SRC (VHF) Marine Radio CourseRYA Short Range Certificate radio course. Study online, then take the practical exam with an RYA assessor.
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      Are you looking for something nautical related? Our directory is an extensive list of courses and places associated with the marine industry. Hop over and search now.

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      • Nautical Terms & Terminology
        Understanding the language of the marine world is like trying to learn a pirate’s secret code while juggling fish. Let us explain why a sheet isn’t for your bed, why “heave ho” doesn’t mean throw up (most of the time), and why “dead reckoning” is surprisingly less ominous than it sounds.
      • Why do we have tides?
        Have you ever wondered what causes the tides? Check out this video, which introduces the forces that create the tides we experience on Earth.
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        A video introducing the drivers behind our weather, part of our RYA Day Skipper & RYA Coastal Skipper / Yachtmaster® Offshore theory courses.
      • Buoyage Flashcards
        Flashcards designed to help remember the buoys in the IALA system. If you want to learn them in detail, our module ‘Getting in and out of harbour‘, covers the IALA system and different buoys used.
      • Interactive Rule Book (COLREGs / IRPCS)
        Whether you’re a novice sailor or a seasoned skipper, we can help you navigate the IRPCS confidently and clearly. Our easy-to-use, easy-to-understand, plain English rule book with helpful interpretations of what each rule means.
      • The Salty Sea Blog
        From salty old sea dogs to fresh-faced deckhands, this blog is for anyone who finds peace, adventure, and a bit of mischief on the water. So hoist the main, set your course, and let’s sail into the stories, lessons, and musings that make life on the sea so irresistible.
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Published:25th October 202419th March 2025 Last Updated:19th March 2025
General Nautical Terminology | Safety

Global Maritime Distress and Safety System (GMDSS)

An internationally agreed-upon set of safety procedures, communication protocols, and equipment designed to ensure that ships at sea can send and receive distress signals and safety information.

The Global Maritime Distress and Safety System (GMDSS) was established by the International Maritime Organization (IMO) to enhance maritime safety and facilitate the efficient coordination of search and rescue operations. It is a comprehensive system that integrates satellite and terrestrial communication technologies to ensure that vessels, regardless of their location, can communicate distress signals and receive urgent safety information. The system is mandatory for all ships over 300 gross tonnage engaged in international voyages, as well as passenger ships, and it is designed to function automatically, reducing the reliance on manual intervention in emergency situations.

GMDSS equipment includes a range of communication devices, such as VHF, MF, and HF radios, satellite communication systems (like INMARSAT), Emergency Position Indicating Radio Beacons (EPIRBs), and Search and Rescue Transponders (SARTs). These devices are used to transmit distress alerts, receive navigational warnings, and communicate with rescue coordination centres. The system is divided into four sea areas (A1, A2, A3, and A4), each with different communication requirements based on the distance from shore and the availability of communication infrastructure.

The GMDSS has significantly improved the safety of life at sea by ensuring that distress signals are relayed quickly and efficiently to the appropriate authorities, enabling faster response times and more effective rescue operations.

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