In his later years Cornel Wilde did a number of films on his own as his day as a box office draw had long gone. Stuff like Beach Red and The Naked Prey were interesting. Sharks' Treasure was quite a bit less in quality than those others were.
Wilde here is a charter boat captain no doubt giving three hour tours like the Skipper and Gilligan did on the USS Minow. Young surfer kid John Neilson brings an old Spanish gold doubloon and he knows where there might be more on the Mexican coast.
Wilde and Neilson take on Yaphett Kotto and David Canary as crew and the four set out for the spot that Neilson says the treasure was found. The four do some considerable diving and then have the misfortune to run across a group of escaped convicts led by Lobo as played by Cliff Osmond who certainly justified his name.
One of the convicts is David Gilliam who looks a lot like Neilson, blond and pretty and Osmond's personal boy toy from prison. Osmond's weakness is Gilliam and Neilson is no doubt grateful Gilliam's around otherwise these guys who haven't seen any female companionship would zero in on him. It all proves their undoing.
The underwater sequences are nice and the sharks as a dangerous as those in the various Jaws films. And the guys are all walking around in various states of undress which no doubt titillated the women and gay men in the audience. Cornel Wilde certainly looked in good shape for a guy in his sixties.
Sharks' Treasure is your routine action film, other than the underwater sequences and the well put together men, nothing more.