COLREG and IALA buoyage, made simple
Navigation lights in 3D, sound signals, GMDSS radio and knots, explained in plain words. Then test yourself.
- Every answer explained, with the rule behind it
- Free simulators: radio, radar, weather and knots
Question 1 of 5Two power-driven vessels in sight meet on reciprocal or nearly reciprocal courses with risk of collision. Under Rule 14, each shall:
Tap an answer to check it
- Every answer explained, with the rule behind it
- Free simulators: radio, radar, weather and knots
What are you studying?
Pick your syllabus. Read the theory, quiz yourself on it, then sit a mock exam when you feel ready.
COLREG
International collision regulations, Rules 1–41
IALA
Buoys, marks and their lights
GMDSS
Radio and distress procedures
Free simulators. Learn by doing.
All free · no sign-up · nothing to download
- Radio simulatorVHF, MF/HF, NAVTEX, EPIRB and SART with guided lessons
- Radar simulatorRelative motion, CPA and TCPA on a manoeuvring board
- Weather labClouds in 3D, front passages and weather charts
- Beaufort simulatorWind forces 0–12 and the sea in 3D
- Signal flag gameLearn the 26 International Code flags against the kraken
- Knot studioTie the bowline and more with a 3D rope, then check your knot
Practice across every topic
Teaching a class? Run one quiz for the whole room, with no accounts needed, or see the tools for teachers.
More to explore
Built for the rules part of your exam
Study the International COLREG rules with source texts, explanations, vessel-light models and sound examples. Practise individual topics or use a timed practice exam.
Start wherever you like. Read a rule, take a short quiz on it, then sit a full mock exam when you feel ready. Everything is free to use, supported by a few ads that only appear if you accept them. We're independent, so we don't sell courses or issue licences. We just want you to walk into your exam feeling prepared.