A great wreck off Portland Bill the M2 is one of my favourite and most dived wrecks.
Location: 50°34'.567 N, 002°33'.916 W
Depth: 33m (seabed)
Type: M Class submarine
The historyThe M2 was one of four submarines originally ordered by the navy that were to be armed with a 12" battleship gun. They used the hulls from the last of the older WWI K-class submarine. M1, M2 and M3 were completed but M4 was cancelled. The M2 was used for various trials including deep diving and resistance to poison gas. She was converted to carry a seaplane, by removing the gun and replacing it with a hanger.
The crew were known to be very keen on trying to shave time off how quick they could launch the plane. On 26th January 1932 she left West Bay for exercises and at around 10.30 she reported read to dive. At around 11.30 the steamship Tyneside allegedly spotted a submarine diving stern first! The M2 was not seen again on the surface.
Eight days later she was found and investigated by navy divers and the salvage operation was taken by Earnest Cox, who had previously salvage the scuttled German fleet at Scapa Flow. However salvage operations were dogged with problems and in December were called off.
It was concluded that the hangar doors were opened too early and the submarine had been swamped.
The wreck site
The wreck sits upright on a sandy seabed at around 33m (so makes it doable on Nitrox 32). Usually the shot line drops you down near the conning tower and onto the top of the hull.
This is my usual route, done on a twinset and stage. Adjust the length of your dive appropriate to your kit (for example you may choose to just do the main hull top if on a single tank).
Heading down over the side brings you to the seabed where heading to the stern you find the propeller shafts, the props were removed on the original salvage attempt. It is possible to duck under the stern in the scour, where it is possible to get a couple of extra meters depth.
Moving forwards it is possible to find some of the remains of the lifting gear off to the sides. At the bow you can again duck underneath the sub but it is worth backing off a little and ascending facing the bow.
Going round again you get to see the forward torpedo tubes where conga can usually be found. Along the side of the sub, at around 28m - 30m, the top of the hull has lots of interesting features though be careful as the deck railings have rusted away leaving sharp spikes. The launch catapult for the plane is encountered and leads back to the conning tower and hangar. Keeping going, behind the conning tower are structures and the foldaway deck gun (see if you can spot it
). Holes allow the diver to peer down into the gap between the outer an inner pressure hulls.
Once you reach the stern head back and end up at the conning tower and hanger. The hanger is mostly filled with silt and so just look but don't enter. Working your way up the side the arm which was used to recover the seaplane is on top of the hangar. The top of the conning tower is around 24m and you can spend a few minutes poking around here.
It is worth drifting slightly off the wreck before bagging off as the masts usually have bits of rope hanging off that could snag a dSMB.
Its quite remarkable how 'sharp' the bow is.