Each question shows a situation, a vessel's lights or shapes, a sound signal or a point of the rules, then opens two to four answers. Pick the right one: the quicker you answer, the more points, from 1000 down to 500, with a bonus for a run of right answers. After each question you see the right answer, the rule it comes from and a short explanation.
At the end your score earns a rank: 70% makes you an Acting Sub-Lieutenant, 80% a Sub-Lieutenant, 90% a Lieutenant and a perfect score a Lieutenant-Commander.
Choose Host a game on a computer or projector screen. Everyone else opens this page on their phone, enters the six-digit code and their name, and joins. The host chooses how many questions, which rule sets and which rules to include, and moves the game on when everyone has seen the answer.
About 470 questions cover every rule of the International Regulations for Preventing Collisions at Sea, 1972 (COLREGs), from Part A to Part F and Annexes I to IV: look-out, safe speed, risk of collision, narrow channels, traffic separation schemes, overtaking, head-on and crossing situations, restricted visibility, navigation lights and day shapes, and sound and distress signals. Optional sets cover Canada's Collision Regulations and the US Inland Navigation Rules.
Want to read up first? See our plain-English guide to the rules of the road.