W007:
Given favorable conditions, (relatively smooth water and no crosswind) ditchings are very possible. If you don't have control problems (unusual attitudes, extreme adverse yaw [engine out], bad rudder damage) and can make a normal approach, you have a very good chance.
The Navy has been known to sink floating planes that didn't have the decency to sink, something about a "menace to navigation".
There are likely hundreds of successful ditchings on record. While you don't practice them, they are usually mentioned in flight school. Navy pilots ARE given training on what to do AFTER the plane stops. For them, its "just another day at the office": i.e. a fact of life in their profession.
And most of the Operations Manuals that I have read have a "Preparation for Water Landing" section (one of the red edged pages).
I sat through a discussion on ditchings and have never done one; now, I wish they had covered blowing a tire...
Mustang