IMAGINE THAT THE M2 disaster never happened. It was a winter’s day in 1932, the HMS M2 submarine had been undergoing her sea trials, and everything had gone well.
The crew got the Parnell Peto seaplane off in record time, and M2’s Captain Leathes was delighted. The Admiralty was also pleased, and recommended further training of the crew to bring them to combat-readiness. M2 would have a forward reconnaissance role within a battle-group of warships.
In the years that followed, M2 and her sister-vessel M3 (converted to a minelayer) were both seen as a showcase of the best of British engineering.
By 1936 the clouds of war were once again building over Europe, and when the conflict finally came, both submarines saw extensive war service and distinguished themselves…
Let’s end the fantasy there. What actually happened was that M2 sank to the depths of Lyme Bay on that day in 1932, taking with her not only her young crew but also the dreams of the boffins who had thought up all those exciting plans for the Monitor-class submarines.
Who knows how and where M2 might have been used, and how useful she might have been?

THE WRECK OF THE M2 lies off the coast of Dorset, and has become a must-do for UK divers progressing past the introductory grades of their training, with a maximum depth of just over 30m depending on the state of tide.
Its decks lie at about 27m, the top of the conning-tower at 20m and the top of the periscope 2-3m shallower. PADI Advanced Open Water Divers and BSAC Sports Divers can both enjoy the wreck to the full.
Submarine wrecks are easy to navigate around – it’s very difficult to get lost. Even if you haven’t listened to the briefing, once on the wreck you should know where you are.
I would recommend listening, however, because skippers know a lot about the wrecks onto which they put divers.
They can tell you about the currents, for example – often it’s easier to bag off the wreck instead of coming back up the shotline, and skippers will let you know their preference.
A submarine pressure hull is a very strong construction, designed to withstand many bars of pressure while submerged. As a result, and despite seawater doing its best to corrode the structure away, a submarine will remain much the same shape as a wreck as it was when operational.
Submarines that have come to grief from hitting mines or being depth-charged may well show some damage, but they too will essentially be little changed.
What you’re going to find, of course, is a long metal tube with a raised conning-tower section. Some divers say that subs are boring because they’re all the same. I disagree. Most wrecks are like scrapyards under water, and what makes them interesting is the story behind them.
Submarines often have the most fascinating back-stories, and although the M2 story is well-known, I hope I can add some detail.
Winston Churchill ordered 20 K-class submarines in 1915, but with many skilled shipyard workers away fighting, only a handful were completed by the end of the war.
The orders for the last four were cancelled in favour of a new type of anti-submarine sub designed by Vickers and armed with a 12in gun that could fire a 385kg shell nearly 12 miles. The two Vickers-built boats became M1 and M2; Armstrong Whitworth built M3 and M4.
M1 was completed before the end of the war but saw no action. She was later lost after colliding with the Swedish collier Vidar in 1925 off south Devon.
M2 and M3 were operational until 1928, when the Washington Disarmament Treaty required that signatories reduce the calibre of their armaments, so their guns were removed.
M2 was converted into the submarine we know, carrying a small Parnell Peto seaplane with the hangar fitted forward of the conning-tower. M3 was converted into a minelayer before being scrapped in 1932 after completion of trials, and M4 was broken up before completion.
Lt-Cdr John Duncan de Mussenden Leathes (known as Snakey Leathes) took command of M2 in November, 1930, and her final patrol was on 26 January, 1932, when she was to undertake aircraft-launch, gun and torpedo exercises in Lyme Bay.
“About to commence exercises” was M2’s last message, received at 11.10am. She was not back in Portland Harbour by 4.15, and the alarm was raised. A flotilla of destroyers sailed out of Portland, desperate to locate the submarine.
Just after midnight the Admiralty announced that: “An object presumed to be submarine M2 has been found three miles west of Portland Bill…”

M2 WAS THOUGHT to have had 48 hours-worth of air, and her experienced crew had Davis Submerged Escape Apparatus (DSEA) available.
In fact the wreck located was not that of the M2. On the evening of 29 January, the BBC broadcast: “The Admiralty regrets to announce… it is no longer possible to hope for the rescue of any of the officers and men on board.”
M2 was finally located on 4 February, when divers from HMS Albury read the letters on the side of the conning tower.
They found the hangar door and conning-tower hatch open but the forward and engine-room hatches closed, confirming suspicions that an aircraft launch had been underway when the disaster occurred.
The cause of the sinking could be determined only through a salvage operation, and this revealed the bodies of two crewmen, Leading Seaman Jacobson in the hangar and Leading Aircraftsman Leslie Gregory on the seabed aft of the wreck – further fuel for the aircraft-launch theory.
M2 was brought to the surface twice, but both times slipped back beneath the waves. Nearly a year after her sinking the salvage was finally abandoned, and M2 still lies on that shingle seabed, upright and intact.
The hangar door is open and all but the outer conning-tower hatch were sealed with steel-plates or concrete during the salvage attempts. The seaplane was also salvaged in 1932.
I first dived M2 in the late 1980s. It was my first 30m dive, and I was excited and a touch apprehensive as I prepared to jump in and make my way down the shotline. In those days I was good and recorded my dives:
May 1988 – The wreck came into view, the shotline was at the conning tower.
I settled on the wreck and adjusted my buoyancy. The wreck was covered with brittlestars, anemones and dead men’s fingers. It looked amazing! My buddy and I went aft, looking into holes. We dropped to the seabed near the propshafts. After this we returned to the conning-tower and went out along the crane. There were lots of fish. Our bottom time was 18 minutes, total dive-time 28 minutes. Max depth was 34m. I was using a single 12-litre cylinder of air. Visibility was about 5m.

THE WRECK I SEE TODAY is essentially the same, though I haven’t seen brittlestars on it recently, and the crane has broken away from the top of the hangar. Interesting features such as the conning-tower with the periscopes heading up to the surface, deck gear and overall form remain essentially unchanged in close to 30 years.
On one of my recent dives to put together this report, I noticed that behind the main periscope is an auxiliary helm, which would have allowed the submarine to be steered from the conning-tower and would have had a wheel in place.
It illustrates that no matter how often you dive a wreck, previously missed features can still come to light. The helm is covered in bright pink jewel anemones.
Forward of the conning-tower is the hangar, and in front of it on deck the seaplane-launching hydraulic catapult. Look around the machinery, as conger eels are often seen lurking behind and peering through holes.
Look more closely still and you’ll see that the wreck is alive with marine life – tompot blennies peeping out with their ridiculous hairstyles, nudibranchs munching on hydroids, sponges, dead men’s fingers, cup corals and a multitude of other species. The deck stretches forward from here and is relatively featureless, but shoals of fish swirl over the wreck structure, most commonly bib or pouting.

WHEN YOU ARRIVE AT THE BOW, if time allows, drop to the seabed. If the vis is favourable, you will have an impressive view, and there is a space through the bow here, where the torpedo-tubes are located. On the side, the stowed anchors remain.
Return to deck level and head aft past the conning-tower, which is covered in swathes of colourful jewel anemones. There is some machinery aft of the tower.
Before long the stern is reached. Drop to the seabed to check out the propshafts. The propellers were salvaged many years ago, before the current rules regarding salvage from sensitive wrecks was established. Check out the hydroplanes as you make your way back to deck-level to bag off or return to your shotline.
Advances in diving technology with the introduction of computers, modern decompression theory, nitrox and rebreathers mean than most divers can spend considerably longer on the wreck than was deemed possible in 1988.
On my most recent dive with a rebreather I had 62 minutes on the M2, followed by 14 minutes of deco.
As you ascend, spare a thought for Captain Leathes and his crew, who still lie entombed within the submarine.
They were sons, lovers, husbands and fathers whose lives were cut short, so this wreck deserves the respect that I’m sure divers will give her.

For divers using their own boat, the marks are 50.35.033N, 02.34.650W and the nearest place to launch is at West Bay, Dorset. Rick Ayrton has also used Portland hardboats SkinDeep, run by Ian Taylor (skindeepdivingportland@ gmail.com) and Scimitar run by Nick Bentall (info@scimitardiving.co.uk).
The SkinDeep shop and gas station is at Portland Marina.