Carradine is a scientist who develops a submersible device for exploring the ocean bottom. While he waits on the boat, a team of divers man the contraption and take it down. After they bash into underwater mountains and coral reefs, they flee the diving bell and take shelter in a fabulous
underwater cave complete with handy air pocket. Before Carradine can rescue the team, volcanic eruptions begin to destroy the cave, and only after one diver is killed by falling rock does Carradine manage to get them to the surface. Low-budget science fiction effort slightly redeemed by
Carradine's gaunt frame.