[Dartskipper]

In reply to Malcolm's post above, when I was on the smaller (76ft) ketch "Orcella" we experienced a sudden influx of water below the waterline when entering the Windward Passage bewteen Cuba and Haiti in 1975. (We were on our way from Fort Lauderdale to the Panama Canal.)
One of the crew reported that his toilet wasn't flushing properly. A quick inspection showed that it was being emptied, but there was no seawater flushing the bowl. A quick dash into the engine room, situated beneath the main saloon, and looking under the deck boards showed a seawater intake hose adrift, and seawater pouring into the bilge. (The Dutch builders had used flexible armoured hoses for seawater intake and discharge, and it was the only occasion when a connection failed.) We hove to and rapidly reconnected and secured the hose, and commenced returning the Caribbean Sea from our bilges to back where it belonged. So, a yacht can suffer sudden influxes of ocean in more ways than an open hatch or window.

I'm certain that the official enquiry will discover exactly what happened, but I just wanted to show that obvious conjecture isn't necessarily correct.