A group of scientists discovers an ancient abbey in a Romanian forest, built over the entrance to a complex system of underwater caverns. With back-up from a team of professional cavers, the explorers plunge into the darkness in a bid to discover what lurks below - but soon regret their curiosity as ferocious monsters begin to surface. Horror, starring Morris Chestnut, Lena Headey and Cole Hauser.

After a group of biologists discovers a huge network of unexplored caves in Romania and, believing it to be an undisturbed eco-system that has produced a new species, they hire the best American team of underwater cave explorers in the world. While exploring deeper into the underwater caves, a rockslide blocks their exit, and they soon discover a larger carnivorous creature has added them to its food chain.