According to Franco Nero, producer Enzo Doria wanted to direct the film himself. But on Nero's insistence, Castellari was hired. The script was written in Italian. An English translation was to be brought over to the shooting location in
Cozumel, in the
Gulf of Mexico, by actor
Eduardo Fajardo, but because his luggage got lost, the shooting started without a script. The story was recreated on the spot. Actor
Michael Forest helped with the English dialogue. The underwater photography was done by Ramón Bravo. According to Nero, sharks were caught at night and put in cages underwater. "The next day we would go in the water with the tanks to film the scenes", Nero said. "The shark would be almost dead. They were harmless, because they had no more strength." ==Release==