Why would landing the space shuttle on water have been unsurvivable?
The shuttle lands at 220 mph and would break up. This is 40% faster than airliners with twice the energy to dissipate and the shuttle structure is a great deal lighter. The orbiters were designed to go to space, ending each mission of their 100 mission lives by landing on a smooth runway. Airliners are designed for forty to a hundred thousand landings or more and they don't always fare that well in water either.



(Youtube - Ethiopian 961)