Submarine operations have long been hazardous and remain so today. A submariner’s hope is always that the boat will surface the same number of times it dives, but sadly this has not always been the case. The last Royal Navy submarine to be lost was the Sidon in 1951, but the Russians and Americans have lost submarines since then, the latest of which was the Kursk in 2000. The first account I have been able to discover of men escaping alive from a sunken submarine was that of the German submarine, U-3, in 1911. I have used some of the facts to illustrate the events in my novel, The Custom of the Trade.
Unfortunately, the Royal Navy was slow to adopt submarine escape equipment, even though Sir Robert Davis, the head of Siebe Gorman and Company Ltd, invented an oxygen rebreather kit in 1910 for use in submarines. However, it was considered too bulky to allow an escaping submariner to exit the upper conning tower hatch and it was only in 1927 that the RN formally adopted the apparatus after some modifications. The apparatus was used with limited success for submarine escape in the 1930s.
Instead, and again in 1910, the RN introduced the Hall-Rees breathing apparatus into submarines. The joint inventors were the then Inspecting Captain of Submarines, Captain Hall, and Surgeon Commander Rees. Unfortunately, many submarine captains deemed that the escape apparatus took up too much space in the already cramped confines of a submarine and landed the kits. I have come across no evidence that the apparatus was ever used successfully. This website gives much more comprehensive information on the Hall-Rees apparatus.
http://www.divingheritage.com/hall-rees-daviskern.html