A couple of times I've rounded the first mark of a race only to be presented with a "wrong way" message. I think it was because I broke the start (or at least I was close enough to think I may have). Perhaps two guns/horn blows from the start boat to indicate that a player has broken the start? Don't necessarily need to tell a specific player that he or she has broken, just an indication that someone has broken and leave it up to the sailor to make their own judgement.