My buddy and I once took out a 20 foot boat sailboat to open ocean which began to sink. The boat wasn't 'taking on water' but rather, THE PLUG WAS NOT PLUGGED IN (Yes, there REALLY was a plug) so the boat sank to below the water line but remained partially buoyant with the plug put back in. Somehow we got that boat to a beach (can't remember what city) and rounded up some guys to help pull the waterlogged boat ashore where we waited for it to drain.
I've got 3 years of childhood swim school under my belt but I would not be here today if that boat sank out in open ocean.