This hysterical drive-in favorite pits a community of swamp-dwelling yokels against the silliest-looking monsters since the shag-rug aliens of The Creeping Terror. Despite the strange sucker-marks found on a dead trapper's blood-drained body, and a man's story of seeing his unfaithful wife and her lover dragged into the swamp by the creatures, the police refuse to acknowledge that something freaky is going on. Only after more trappers disappear does the local game warden decide to take action, which he does with a vengeance. When the leech lair is discovered in a cave beneath the swamp, explosives are employed to blow them to little rubber bits. It's hard to be too critical of this early film from prolific TV-director Bernard L. Kowalski (Night of the Blood Beast), since executive producer Roger Corman allocated a budget for this production that would hardly cover the catering bill on a major studio film -- even in 1960! Look carefully to spot the scuba tanks beneath the leech costumes.
~ Cavett Binion, All Movie Guide