The Watch Below

Doc Radford, the Exec, Wallis, and First Officer Dickson, together with two badly injured and hysterical nurses... all of them stuck in the pitch dark, bleak cold of a hull several fathoms under water.
Unkind chance, instead of killing them, had left them with oxygen tanks and stores of food.
Somehow they had to find a way to stay sane long enough to make a new home in this strange environment.