Ah, good to know. (My confusion was genuine, BTW: I knew "leech" means the back edge of a fore-and-aft rigged sail, so it wouldn't have surprised me if it also meant the back edge of a wake or something like that.)
An event like that held somewhere in the US these days would likely result in pages of documented collisions and other incidents. But that’s likely because:
Most states don’t require any sort of licensing or training in safe operation of boats, or at least a very minimal level.
Many boaters in the US seem to think it’s perfectly fine to operate boats while drinking alcohol…
Seriously, though, it just appears to me that it wouldn't take much to turn that situation into a tragedy but I don't know a darn thing about sailing. I went one a few charity motorcycle rides and they felt the same: too many people who's abilities are unknown and mostly likely more than a few who were drinking.