an on screen caption informs u that it be the caribbean sea and may 1891. a small lifeboat drift aimlessly at sea contain six convict from a shipwrecked prison ship and and the ship doctor a lt. claude de ross ( claudio cassinelli ) . it night and a strange current take the boat towards a strange and unnamed and uncharted island . the boat hit some rock and be torn apart . one of the prisoner be kill by what appear to be a slimy mutant fish man creature . the next morning morning claude wake up to find himself wash upon a beach . he find a pool of white bubbling water and one of the prisoner dead beside it . claude warn another survive prisoner jose ( franco iavarone ) not to drink the water a it will kill him . they both eventually meet up with the other survive prisoner and peter ( roberto posse ) and francois ( francesco mazzeri ) and skip ( giuseppe castellano ) . francois wanders off on his own to try and catch an animal for food and he find and kill a large water bird . but in turn he be kill himself by one of the fish men . claude and jose and peter and skip continue to explore the island a they put francois death down to an animal attack of some sort . soon after skip be kill when he be impale on a spike at the bottom of a pit . now only claude and jose and peter be leave . they stumble across a cemetery with lot of empty graf and sign of recent black magic ritual . claude spot a snake on a nearby rock and suddenly a shot be hear and the snake head explodes . a woman on horseback name amanda marvin ( barbara bach ) be reveal to be claudes saviour . she tell them to leave the island immediately a it be own by a edmund rackham ( richard johnson ) and he doesn not like visitor . claude and jose and peter decide to carry on regardless and eventually find rackham large house in which they be invite to stay . that night peter go after amanda and try to rape her in a swamp and peter quickly become food for the fish men . and a voodoo priestess call shakira ( beryl cunningham ) and who live with rackham and perform a black magic ritual involve slit the throat of a chicken at the cemetery . the next day claude and jose decide they should leave the island a they feel very uneasy about rackham and think he be lie to them . jose ride off on horseback and be lose . claude be save from one of the fish men by amanda and be again tell to leave . claude want to confront rackham again . rackham reveals that he have a scientist and and amanda father and name professor ernest marvin ( joseph cotten ) who he need to be keep alive . rackham say that the long ernest stay alive the chance of his own survival will dramatically increase . rackham tell claude his plan . rackham have find the lost city of atlantis at a depth of over 2 and 000 foot . he be use the fish men a a mean of get at the lost treasure of atlantis and and need amanda and her father to control them . he claim the fish men be descendant of the original inhabitant of atlantis . rackham offer claude a share of the treasure if he will help him keep ernest alive . later claude remembers the name ernest marvin a a scientist who be condemn for experiment transplant animal organ into human being . find ernest secret laboratory he discover rackham have lie to him and the fish men aren not descendant and their actually genetically altered people turn into amphibious creature by ernest grotesque experiment . rackham have finally have enough of claude and decide to put an end to his meddling by stick him in a large tank and slowly fill it with water and a the island volcano start to erupt and send lava fly everywhere . rackham want to leave the island with his treasure and amanda and will claude escape almost certain death to save amanda and get off the island before the erupt volcano tear it apart . direct by sergio martino i really like this film that mix various genre . the script by sergio donati be fast paced and interesting and entertain . the plot be reveal bit by bit and which keep me interested in watch it all the way through . i must say at this point that i have see the original version and not the one with added scene insert for it u release by roger corman . barbara bach make for an extremely attractive lead lady and but i hat the way she be introduce by shoot a snake head off and i think it be more than a little distasteful . richard johnson make a great villain and claudio cassinelli a likable hero . the fish men themselves look a little fake when the camera linger on them too long but their cool look and i have see bad . some of the miniature effect look a little poor too and but overall again i have again see a lot bad . there no real gore and violence or nudity in it and but that do not really bother me actually . the photography by giancarlo ferrando and the production design by massimo antonello geleng combine to create a very nice look film . period costume and prop and set like rackham house and ernest lab with it old scientific equipment . the lush green jungle setting also add to the visual splendour on show . i really like this film and i be entertain throughout it run time . i be not sure who i would recommend it too a it mix various genre and i guess someone who maybe fancy something a little bit different and generally well make . if you can find a copy give it a go and i be glad i do .