And there are moments of great beauty. When the submarine is running on the surface, you can stand on the bridge, at the top of the fin, looking down as water pours over the surface of the nose, ripped ragged by the gaps in the soundproof black tiling. At night, in a high winter sea, says the captain, Andy Coles, this can feel like the loneliest place on earth - with great icy spouts of water known as "goffers" surging up the front of the fin, and drenching the man on watch to the skin.