For those piling into a downwind mark in company it has always been a problem to decide when your obligations if any begin. By the time you have thought about it, it is usually too late. Or that had been the case until the 200-1012 ISAF Windsurfing Competition Rules were issues.
The guys on ice sleds however have solved the problem in an eminently simple way. They just lay the mark and then mark out a large circle around it...
Here's the WISSA rule # 4.3.1
"The first sailor entering the mark circle perimeter has the right-of-way. The Mark Circle is an area 10 meters in diameter around the mark. This circle may or may not be physically marked on the ice or snow.'
Pretty clear when the circle has been marked out!
May be one day, we'll have the ISAF Water & Ice Windsurfing plus Kiteboarding Committee!