In the dead of night the U-616 – a Type VIIB U-Boat patrolling the British mainland in the early years of World War II – rescues a solitary survivor from a sunken ship. His story is so outlandish as to be unbelievable: a colossal shark – far too large even to be a Great White – hunting them for days before savaging straight through their hull and sinking them down into the ocean. Captain August Krauser is sceptical of the man’s story, but as the U-616 continues its patrol he is forced to admit that the danger lurking in the water is very real. Something impossibly large and ancient follows the submarine, bringing the two greatest hunters the North Sea has ever seen into an explosive confrontation.
