It depends largely on the type of airplane: Best case scenario: A plane with floats or seaplane, of course. Second best: A high-wing airplane with retractable gear. Worst case: Low-wing airplane with fixed gear. read more
In the case of an airliner, there are two main dangers to take into account: a very high gliding speed and two to four large engines which will bring the airplane to a full stop in a very short lapse of time (or most probably tear the wings apart). read more
being in a plane as it crashes (particularly in the ocean) post-crash, watching the plane sink below the surface of the ocean; being injured in the open ocean ; But anyways, depending on how fast the plane is moving, it's pretty likely that the plane would break apart upon hitting the water. read more