[1] On a deserted beach, four boys, Miki, John, Ben and Allan, are told by an Indian the story of the monstrous marine being Wakan and seal a blood pact, a bond of their friendship and mutual assistance in case of danger.

Their task will not be easy, since a legend says that the beast is an incarnation of an ancient hoodoo spirit that has taken the form of a killer shark.

The boys set an underwater trap for the shark and lure it into an area in which they have planted powerful explosives, thereby successfully killing the beast.

Joe D'Amato met Raffaele Donato in 1975 on the set of Red Coats and used him repeatedly as an English dialogue coach.

[1] He encountered him again years later in the United States and hired him on Deep Blood because he needed someone who was fluent in English.

(...) The actual underwater scenes though were shot in various places: at Ventotene, in a Roman swimming pool and in a New Orleans aquarium.