HMS Perseus was one of six Parthian class submarines (Parthia, Phoenix, Proteus, Poseidon, Pandora, and Perseus). Great Britain launched the program to construct these submarine in 1927. HMS Perseus was laid down on the 2nd of July in 1928, at the Vickers Armstrong shipyards, in Burrow-in-Furness. Launched on the 22nd of May in 1929 and commissioned for service on the 15th of April in 1930. She initially saw service in the Chinese sea and subsequently in 1940 was ordered to join the 1st Sub Flotilla at Aden and then proceed to Alexandria.

On the 6th of December in 1941 whilst the submarine is patroling on the surface south of the island of Kefalonia a huge explosion rocks the submarine leading to its sinking. After being in service in the Mediterranean for eight months HMS Perseus was lost becoming an underwater grave for 61 men. Only one of the 61 men onboard was able to escape and tell the story. This was John Capes who was in the aft compartment and using a Davis apparatus managed to escape from the sunken submarine. He swam to Mavrata village in Kefalonia where the locals hid him for several months until he was finally returned to British forces via Smyrna. 

The submarine rests on the sea bed at a depth of 52 meters with an 18 degree list to starboard. On the port side of the submarine, near the bow, there is a breach, caused by the exploding mine.

Source: Thoctarides & Bilalis, Shipwrecks of the Greek Seas-Dive into their history, Athens, 2015.