HMS M2 Submarine

Image credit: Wikimedia Commons

Overview

The HMS M2 is one of the most unique and historically significant wreck dives in the United Kingdom. Originally constructed as an M-class submarine during the First World War, the vessel was later radically modified by the Royal Navy to serve as an experimental undersea aircraft carrier. She was fitted with a massive, watertight hangar designed to house a small Parnall Peto seaplane. Tragically, in 1932, the HMS M2 sank during a training exercise off the coast of Weymouth, Dorset, taking her entire crew of 60 men down with her. The sinking was ultimately attributed to water entering the hangar doors while they were open on the surface.

Today, the M2 sits perfectly upright and largely intact on a sandy seabed. The maximum depth at the scour holes near the hull is approximately 35 meters (115 feet), while the highest point—the top of the conning tower—rests at roughly 25 meters (82 feet). Due to the depth and the often-challenging conditions of the English Channel, this site is strictly reserved for advanced and technical divers. It is entirely inappropriate for novices or those undertaking an open water course. For highly experienced divers looking for the best places to learn deep wreck protocols, the M2 represents a benchmark UK dive.

The Dive Experience

The M2 is typically accessed via hardboat charters or large RIBs departing from the nearby ports of Weymouth or Portland. The transit time to the site is generally between 45 minutes and an hour.

Because the wreck is located in the open waters of the English Channel, the area is subject to fierce tidal streams. Diving the M2 is strictly limited to slack water periods, which the charter skippers calculate meticulously. Descending the shot line is a highly atmospheric experience; the dark, imposing shape of the submarine slowly materializes from the gloom.

Visibility can fluctuate wildly, ranging from an atmospheric 2 meters on a poor day up to 15 meters on a pristine summer tide. Water temperatures are distinctly cold, generally hovering between 10°C and 14°C (50°F to 57°F) during the diving season. As mandated in cold-water travel and packing literature, diving the M2 requires a drysuit and redundant breathing gas supplies to safely manage the depth and potential for decompression obligations.

What You’ll See

Despite the tragedy of her sinking, the M2 is a breathtaking sight. The submarine looks almost as though she is still actively cruising along the seabed. The most iconic feature of the dive is the massive seaplane hangar. The hangar doors remain fixed open, allowing divers to swim over the threshold and peer into the cavernous space where the aircraft was once stored.

Forward of the hangar, the catapult mechanism used to launch the seaplane is still visible. The conning tower and the large periscope shears dominate the upper sections of the wreck.

Biologically, the M2 functions as a thriving artificial reef. The hull is densely populated with plumose anemones. The wreck is continually swarmed by massive shoals of pouting (bib) and poor cod. Deep in the scour holes beneath the hull and inside the torpedo tubes, divers can frequently spot massive conger eels and large European lobsters sheltering from the current.

Planning Your Dive

Diving the M2 requires advanced booking with Weymouth-based charter boats, as trips are highly dependent on favorable tides and weather windows.

Safety Note: The HMS M2 is classified as a “controlled site” under the Protection of Military Remains Act 1986. While diving on the exterior of the wreck is permitted, it is a designated war grave. Divers are legally prohibited from penetrating the hull or removing any artifacts, and must treat the site with the utmost respect.