1891: Stalwart, morally upright military doctor Lieutenant Claude de Ross (solid Claudio Cassinelli) and several other shipwreck survivors wash ashore on a remote tropical island that's governed with an iron fist by the ruthless and sadistic Edmund Rackham (superbly played to the deliciously slimy hilt by Richard Johnson), who lives on the island with the feisty Amanda Martin (a winningly spunky performance by the ravishing Barbara Bach) and her unhinged rogue biologist father Professor Ernest Martin (a marvelously dotty portrayal by Joseph Cotten). Moreover, de Ross discovers that Professor Martin has control over a dangerous race of fishman beasts who are being exploited as slave labor by Rackham. Director/co-writer Sergio Martino relates the lively and absorbing story at a constant snappy pace, offers a flavorsome evocation of the lush and remote tropical setting, does an expert job of creating and maintaining a creepy and mysterious atmosphere in the spooky opening third, further spices things up with a nice line in dry humor, and stages the exhilarating action-loaded climax with considerable rip-roaring aplomb. While the central premise is obviously inspired by "The Island of Dr. Moreau," the story nonetheless is given a great deal of freshness and intrigue because of Martino's artful melding of such diverse elements as voodoo, the lost underwater city of Atlantis, a rousing mondo destructo climactic volcanic eruption, buried treasure, unscrupulous genetic experiments, and even some exciting rough'tumble fisticuffs between de Ross and Rackham during the thrilling conclusion into an altogether dynamic, imaginative, and often immensely entertaining whole. The sound acting by the sturdy cast qualifies as another substantial plus: Cassinelli makes for a likable hero, Johnson essays his juicy villain part with supremely lip-smacking aplomb, Bach rates as a quite fetching damsel in distress, plus there are neat supporting contributions by Beryl Cunningham as sinister voodoo priestess Shakira, Franco Iavarone as the superstitious Jose, and Roberto Posse as surly troublemaker Peter. Giancarlo Fernando's sumptuous widescreen cinematography delivers a wealth of striking visuals while Luciano Michelini's throbbing tribal score hits the funky spot. The amphibious humanoid fishman creatures are pretty gnarly-looking, too. An extremely fun flick.