An earthquake doesn't just shake up Southern California -- it awakens a nest of monsters lurking in the Salton Sea. These bloodthirsty sea snails are gobbling up anyone who sets foot in the water. And when the creatures move on to land in search of wider hunting grounds, they launch a reign of terror that threatens to spread across the whole country. Humanity's only hope rests on a crew of intrepid scientists and Lt. Cmdr. John Twillinger (Tim Holt).