conventional boats in the world for their day. Long patrol endurance was a primary design requirement of the Porpoise Class, and the snort equipment was designed to give maximum snort charging facilities and to operate in rough sea conditions in any part of the world. When required, oxygen replenishment and carbon dioxide and hydrogen eliminators made it possible for the class to remain totally submerged for several days without 'snorting'.
When snorting, these submarines remained submerged for as long as six weeks. They were fitted with apparatus to distil freshwater from sea-water for drinking purposes, and this, together with stowage capacity for large quantities of stores and provisions, enabled them to remain independently operational for months without any outside support. With this ability to stay
