Pan American lost a stratocruiser in the Pacific, I cannot remember why but in the back of my mind, they had time to plan the ditching, and again I believe there were no serious injuries.
Looks like it was Clipper 943,
Sovereign of the Skies, N90943, operating PAA 6 on October 16, 1956.
Here's a recent remembrance from the SFO Chronicle:
Danville pilot has historical predecessor
More here:
Pan Am Flight 943 - Wikipedia, the free encyclopedia