There you are, plowing along on a dinghy or windsurf board, when a foiling windsurfer comes roaring up on a collision course* with you, coming from downwind of you, but on the same tack as you.
What to do? Turns out, the foiler has right of way**, because they're downwind, and on the same tack. Even though theyre going way faster than you are.
Best move is to head up sharply, to avoid the collision. If you're lucky, once you head up you'll be on the same course as them, and you will then have right of way because they'll be overtaking you.
In any event, always do what you can to avoid a collision, and try to forgive foilers for going so fast.
*always keep a careful eye out for anyone on a collision course with you. Look for others who are getting closer while appearing to stay in the same place relative to objects that are far away (same compass course).