COLREGs — rule by situation
Pick four parameters: your vessel, the other vessel, the encounter (head-on / crossing / overtaking), and the visibility. The picker returns the applicable rules and the required action — useful for STCW oral-exam preparation or a quick refresher on watch.
Always cross-check with the full text of the COLREGs and with your ship's own instructions; this is a study aid, not an authority.
When to use this tool
Quick answer on watch during a novel encounter — e.g. is the CBD (constrained by draught) vessel the give-way or stand-on when crossing a sailing vessel in restricted vis? Study aid for STCW oral-exam preparation. NOT a substitute for reading the COLREGs directly.
Regulatory basis
COLREGs 1972. Rule 18 (Responsibilities between vessels) sets the master hierarchy: not-under-command, restricted-in-ability-to-manoeuvre, constrained-by-draught, fishing, sailing, and power-driven. Rules 13-17 govern specific encounter geometries. Rule 19 applies in restricted visibility.