The rule governing an overtaking boat is quite simple. The overtaking boat must keep clear.
When you think about it, it’s the obvious thing to do. If you are approaching and catching another vessel from behind, you have it clearly in your sight. The skipper of the boat you are overtaking on the other hand will be keeping a lookout all around, including behind but most of the time will be focused on where the boat is heading.
As you draw closer, you will have to decide whether you will be able to go above it, i.e. to windward, or below it. If you’re sailing hard on the wind, it’s likely that you will need to spring the sheets and ease away below. Doing so will mean that you will gain boat speed. Hopefully this will result in your sailing through the other boat’s wind shadow quickly.
Meanwhile, if you are the skipper of the boat being overtaken, you must maintain your course and allow the overtaking boat to pass.
And what if you’re not sure whether you are an overtaking boat? In Rule 13 of the COLREGS (International Regulations for Preventing Collisions at Sea) it states that:
(c) When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly.
This rule governing the overtaking boat is just one of the Rules of the Road that are illustrated in our self-paced learning and self-test program, the Nautical Knowledge.