Nine cave divers (including Cole Hauser, Piper Perabo and Lena Headey) encounter flesh-eating eels, scorpions, fish – and nasty winged demons.

The scene in which Perabo dangles from a rope while the beastie swoops on her is comically overwrought and the script (‘They weren’t eaten by the creatures – they are the creatures!’) shows the film has its tongue firmly in its cheek.

Even though the twist ending is a cheat, it doesn’t spoil the fun and the thrilling action above and below water level rarely lets up.