Poseidon - China's Secret Salvage of Bri

Royal Navy submarine HMS Poseidon sank in collision with a freighter during routine exercises in 1931 off the Chinese coast. Thirty of its fifty-six-man crew scrambled out of the hatches as it went down. Of the twenty-six who remained inside, eight attempted to surface using an early form of diving equipment five of them made it safely to the surface in the first escape of this kind in submarine history and became heroes.