"Parbuckling" is the righting of a sunken vessel by applying leverage to rotate the vessel into an upright position from one where it is either on its side or fully inverted.

http://en.wikipedia.org/wiki/Parbuckle_salvage

Google it today and it is all about the Concord Concordia.

As a sailor I believe I have employed the technique at least once when my little beach cat went over... and I had to stand on the lower hull to pull the upper hull back down to the water, easy enough to do with a small cat... no doubt a major pain for anything remotely large.