HMS POSEIDON (Lt Cdr B W Galpin) sailed from the UK in November 1930 for the Far East with HMS PANDORA and HMS PROTEUS. On 9 July 1931, POSEIDON was exercising off Wei Hei Wei when the Chinese freighter SS Yuta approached on the submarine port beam. After a series of manoeuvres by both vessels, the freighter collided with the submarine and cut a large V shaped hole in her pressure hull a few feet forward of her gun tower.

The Commanding Officer on the bridge of POSEIDON ordered the crew to abandon ship. The submarine sank in under two minutes in 120 feet of water. The forends and engine room had been isolated as a result of the order to shut bulkhead doors. 18 men were in the after compartment, 8 in the forward compartment. Those in the centre of the submarine escaped through the conning tower before the submarine sank (many climbed directly onto the Yuta). 5 of the eight in the forward compartment escaped using the Davis Submerged Escape Apparatus. The 18 in the after compartment perished.