Porter receives a radio distress call from Bill Darmon, the victim of a shark attack. Darmon is far out to sea and in need of an immediate blood transfusion. Porter radios Miami for blood then sets off to locate Darmon's boat. When the plasma arrives at Darmon's boat, a mishap causes the container to tumble to the bottom of the sea in waters too deep for human diving. Flipper is brought in via helicopter and retrieves the plasma just in time to save Darmon's life.