Source
Rule text: Convention on the International Regulations for Preventing Collisions at Sea, 1972, as amended. This is a study retelling and does not replace the official IMO publication.
How to study
Read the «Rules» section through, then work the «Lights & shapes» diagrams from three angles, then drill the flashcards 10 minutes a day. Progress stays in your browser and is never sent anywhere.
Offline
Press «Add to home screen»: the page installs as an app and opens with no connection. Useful at sea, where there is no signal.
Source, method, updated
Rule wording follows the Convention on the International Regulations for Preventing Collisions at Sea, 1972, as amended (printed edition: Morkniga, Moscow, 2010, ISBN 978-5-903080-73-1). Every rule here is a study retelling with the convention wording quoted alongside; the diagrams are drawn from the text of Part C. It does not replace the official IMO publication. Checked against the source and updated September 8, 2026.