I think DaveRo has pointed the way to the physics of what happened: boats were travelling at more-or-less right angles to one another, and when the ridge of one wave met the ridge of another, the water piled up doubly and overwhelmed the small boats. Add to this the notion that one won't need a life jacket on a nice, slow ride, and there's trouble afoot.

I'm reminded of a disaster some years ago when a rumor started that tickets would not be collected for a big football match in England. A huge crowd formed, pressed against steel fences, and people were crushed to death. The moral is that when many people decide to be naughty, naughtiness can lead to tragedy.

With the boat rally, nobody knows how many boats were there or how many were big or small. But with all those boats close together, when some people decided to go perpendicular to the prescribed path (probably at high speed), they created dangerous, choppy conditions that sank five boats, endangered others, and caused an unknown number of boats to hit rocks.

I'm glad nobody was hurt or drowned, but I'm sure those who needed to be rescued are not sleeping peacefully yet.