Cyclone (movie, 1978)

An airplane goes down in the ocean during a storm and a few survivors find refuge on a small tour boat. Swept out to sea, these people slowly starve to death in the hot sun with barely any food or clean water. With no place to turn, the boat survivors resort to cannibalism to stay alive...that is ..until the rescue planes come to pick them up and the man eating sharks decide its time to eat as well.