The M2 submarine was built by Vickers and launched in 1919 after 3 years in construction. She was an M Class submarine and had an enormous 12” 40 cal Mark IX gun. This gun was removed in April 1928 when she was converted to carry a Parnall Peto seaplane. The wingspan of the plane was 28 ft and folded to 8 ft in order to fit it in the hanger.

Displacement: 1,594 tons Length: 295 ft 9 in (90.14 m) Beam: 24 ft 8 in (7.52 m)

Installed power: 2,400 hp (1,800 kW)   (2 x 12 cylinder ‘Vickers’ Diesel Engine) & 4 Electric motors

2 × 3-blade, 5 ft 10 in (1.78 m) diameter propellers

Speed: 15 kn (17 mph; 28 km/h) (surfaced) 8–9 kn (9.2–10 mph; 15–17 km/h) (submerged) Range: 2,000 nautical miles (2,300 mi; 3,700 km) at 15 kn Test depth: 200 ft (61 m) 

She accidentally reached 239 ft (73 m) in 1923 without any problems  during testing.

On 26 Jan 1932 she left Portland on exercise and her last message was to her Support ship ‘Titania’ telling them she was about to dive. She never returned to Portland and was reported missing that evening by a merchant ship entering Portland harbour. Eight days after the loss she was located by Navy divers and Ernest Cox (The expert who salvaged the German Fleet in Scapa Flow) started a year long unsuccessful salvage operation. At one point the bow was within 6m of the surface. They did manage to recover the plane. The remains of the 60 man crew still lay within the submarine today and were joined by an amateur diver who also entered the submarine and never returned. The cause of the accident is not clear but it is believed the hanger door and hatch were opened too soon during surfacing as they were found open by the salvors.

The hanger hatch was still open when I visited the wreck in the 1970’s but was silted over when I re-visited the wreck in the 90’s. 

Today the wreck is a Protected site and lies in upright. Holes are beginning to appear in the outer hull but she still looks very much like a submarine.

The following photos show the Rudder and Conning tower with its array of marine life. (Photo/Video Steve Clarkson)