In the swamps a drunk poacher sees one of the creatures and shoots at it. No one believes him. Later he shows up half-drained of blood. Then more people start to disappear. One of them is a two-timing wife (who may or may not deserve what she gets). The new ranger is the designated hero. On a diving expedition down one of the lagoons they discover an underground cavern-and a lot of dead or dying bodies. The leeches aren't entirely bad looking, though in a few shots look like divers with big plastic bags over them. In the end they blow them up with dynamite and the giant leeches come floating to the surface.The best scenes of this movie are when they show the leech victims moaning and screaming in this underground cavern as the giant leeches feed on them. This scene has always stuck in my mind since I was a kid. Unfortunately, the rest of the movie doesn't quite equal that reaction.