A group of biologists discovers a huge network of unexplored caves in Romania. The biologists believe they have found an undisturbed eco-system that has produced a new species. They hire the best American team of underwater cave explorers in the world. The team is so excited about the new cave that they start the dive immediately along with the biologists. While exploring deeper in the underwater caves, a cave-in blocks their exit, so they must find a new way out. They soon discover a larger carnivorous creature has added them to its food chain.
