An on screen caption informs us that it is 'the Caribbean Sea, May 1891'. A small lifeboat drifts aimlessly at sea containing six convicts from a shipwrecked prison ship, and the ship's Doctor a Lt. Claude De Ross (Claudio Cassinelli). It's night, a strange current takes the boat towards a strange, unnamed and uncharted island. The boat hits some rocks and is torn apart. One of the prisoners is killed by what appears to be a slimy mutant fish-man creature. The next morning morning Claude wakes up to find himself washed upon a beach. He finds a pool of white bubbling water and one of the prisoners dead beside it. Claude warns another surviving prisoner Jose (Franco Iavarone) not to drink the water as it will kill him. They both eventually meet up with the other surviving prisoners, Peter (Roberto Posse), Francois (Francesco Mazzeri) and Skip (Giuseppe Castellano). Francois wanders off on his own to try and catch an animal for food, he finds and kills a large water bird. But in turn he is killed himself by one of the fish-men. Claude, Jose, Peter and Skip continue to explore the island as they put Francois's death down to an animal attack of some sort. Soon after Skip is killed when he is impaled on a spike at the bottom of a pit. Now only Claude, Jose and Peter are left. They stumble across a cemetery with lots of empty graves and signs of recent black magic rituals. Claude spots a snake on a nearby rock, suddenly a shot is heard and the snakes head explodes. A woman on horseback named Amanda Marvin (Barbara Bach) is revealed to be Claudes saviour. She tells them to leave the island immediately as it is owned by a Edmund Rackham (Richard Johnson) and he doesn't like visitors. Claude, Jose and Peter decide to carry on regardless, eventually finding Rackham's large house in which they are invited to stay. That night Peter goes after Amanda and tries to rape her in a swamp, Peter quickly becomes food for the fish-men. And a Voodoo priestess called Shakira (Beryl Cunningham), who lives with Rackham, performs a black magic ritual involving slitting the throat of a chicken at the cemetery. The next day Claude and Jose decide they should leave the island as they feel very uneasy about Rackham and think he is lying to them. Jose rides off on horseback and is lost. Claude is saved from one of the fish-men by Amanda and is again told to leave. Claude wants to confront Rackham again. Rackham reveals that he has a scientist, and Amanda's father, named Professor Ernest Marvin (Joseph Cotten) who he needs to be kept alive. Rackham says that the longer Ernest stays alive the chances of his own survival will dramatically increase. Rackham tells Claude his plan. Rackham has found the lost city of Atlantis at a depth of over 2,000 feet. He is using the fish-men as a means of getting at the lost treasures of Atlantis, and needs Amanda and her father to control them. He claims the fish-men are descendants of the original inhabitants of Atlantis. Rackham offers Claude a share of the treasure if he will help him keep Ernest alive. Later Claude remembers the name Ernest Marvin as a scientist who was condemned for experiments transplanting animal organs into human beings. Finding Ernest's secret laboratory he discovers Rackham had lied to him and the fish-men aren't descendants, their actually genetically altered people turned into amphibious creatures by Ernest's grotesque experiments! Rackham has finally had enough of Claude and decides to put an end to his meddling by sticking him in a large tank and slowly filling it with water, as the islands volcano starts to erupt and send lava flying everywhere. Rackham wants to leave the island with his treasures and Amanda, will Claude escape almost certain death to save Amanda and get off the island before the erupting volcano tears it apart? Directed by Sergio Martino I really liked this film that mixes various genres. The script by Sergio Donati is fast paced, interesting and entertaining. The plot is revealed bit by bit, which kept me interested in watching it all the way through. I must say at this point that I've seen the original version and not the one with added scenes inserted for it's US release by Roger Corman. Barbara Bach makes for an extremely attractive leading lady, but I hated the way she was introduced by shooting a snakes head off, I thought it was more than a little distasteful. Richard Johnson makes a great villain and Claudio Cassinelli a likable hero. The fish-men themselves look a little fake when the camera lingers on them too long but their cool looking and I've seen worse. Some of the miniature effects look a little poor too, but overall again I've again seen a lot worse. There's no real gore, violence or nudity in it, but that didn't really bother me actually. The photography by Giancarlo Ferrando and the production design by Massimo Antonello Geleng combine to create a very nice looking film. Period costumes, props and sets like Rackham's house and Ernest's lab with it's old scientific equipment. The lush green jungle settings also add to the visual splendour on show. I really liked this film and I was entertained throughout it's running time. I'm not sure who I'd recommend it too as it mixes various genres, I guess someone who maybe fancies something a little bit different and generally well made. If you can find a copy give it a go, I'm glad I did.