Unless there's more information I don't know about, all that was said is that whales were ramming the rudder, they were taking on water and the boat sank.

I would think that if whales were ramming the rudder they were also ramming the keel, hull and prop shaft.

6 minutes is really fast for a hole from a rudder post as the only way water was coming in. It would be interesting to see the hull and what the damage was. Guess that will never happen.