A bunch of people go to the island of Mora Tau. Right off the coast of it, a ship sank with diamonds aboard and they want them. There's nice guy Jeff Clark (Gregg Palmer), Dr. Eggert (Morris Ankrum), George Harrison (!!!) (Joel Ashley) and his slutty wife Mona (the immortal Allison Hayes). What they don't know is that the ship is guarded by zombies who kill anyone who tries to take the jewels.
Admittadely novel idea is almost completely destroyed by a silly script and some pretty bad acting. The "underwater" scenes are actually pretty hysterical. They're obviously shot on a sound stage with the actors moving very slow and having bubbles pour out of their diving suits! Notice how the plants on the "ocean" floor never move.
Still I have a certain fondness for silly movies like this. It takes me back to my childhood where these popped up on Saturday afternoon TV constantly. It does have a little creepy scene when the zombies attack at the end and Hayes (a seriously under rated actress) is very good in a nothing role. Also I saw a nice, clean, letter-boxed (!) version of this on TCM. Silly but fun.