In 1942, to frustrate the Nazis decimating the Atlantic convoys, the US Navy plans to capture a stricken U-boat - carrying the Enigma coding device - with a fake German rescue sub. The operation goes disastrously wrong. However, Lt Tyler (McConaughey, sonambulent), a popular but frustrated officer, proves his worth by navigating the U-boat plus its vital device into safe waters. Aided by persuasive effects and authoritative production design from Götz (Das Boot) Weidner, writer/director Mostow pays his dues to the genre, but without much charge and even less depth. After an overextended landlocked prologue, the film pits Tyler and his sub against the German navy in a series of efficient if predictable cat and mouse encounters. A natural climax eludes the film-makers and instead an endnote asks us, with some gall, to view this Americanised composite as a tribute to largely British actions during WWII.