Submarine: Life Under the Waves follows the crew of nuclear-powered HMS Trenchant as they set sail on 120 of tense and dangerous underwater operations. For the first time ever, the top-secret world of the hunter-killer submarine will be revealed as we explore how the crew of 100 men survive underwater for so long in cramped and confined spaces. At depths of over 400m in the North Atlantic, HMS Trenchant must deal with engine fires, poisonous air and food shortages as they're tasked with defending the British Trident nuclear deterrent from Russian nuclear submarines, and gathering secret intelligence off the coastline of Russia.