Wreck Tour 81: The M-343

The M343 Wreck Tour
The M343 Wreck Tour

How often do you get the chance to dive a German surface warship in the Channel? JOHN LIDDIARD provides a tempting taster. Illustration by MAX ELLIS

THIS MONTH’S TOUR takes us back to the wartime wrecks of the Channel Islands and the Kreigsmarine patrol vessel M-343. It's a rare chance to dive a purpose-built German warship of World War Two other than a U-boat.

Also read: Above 18m: Diving Jersey’s Bouley Bay

The wreck of the M-343 is broken in two, with the stern part upright on the flat-bottomed hull and the more V-shaped bow part a few metres away and fallen to port. Unlike ships of the Royal Navy, these German patrol vessels were not required to weather Atlantic storms, and the hull shape exhibits a different compromise between sea-keeping ability and speed, with the emphasis on speed.

The highest point of the wreck is the starboard side of the bow, so that is where our tour begins at 27m (1). Dropping to the keel at 30m, debris inside the wreck includes broken wine bottles (2).

The break in the wreck steps down through the decks of the bow. Moving up one deck, a coil of cable has fallen to the seabed (3), then, a little forward, another step between decks provides an opening into the forepeak (4).

Another coil of cable has fallen to the seabed with the shaft and head of the starboard anchor capstan, while the port capstan is still firmly in place in the bow deck (5). Just off the bow, the starboard anchor rests in its hawse pipe flat against the seabed (6).

The stern part of the wreck is separated from the bow by 10m or so, though not in the immediately obvious direction in line with the keel. From the break, the direction to the stern is perpendicular to the keel.

Across a debris field consisting of bits of deck and hull, the first distinctive item is a gun pintle (7), just off the port side of the stern.

Gun pintle from the main 105mm gun on the M-343
Gun pintle from the main 105mm gun

Inside the port side of the hull is one of the high-pressure water-tube boilers (8) that fed the M-343’s steam turbines.

The usual boilers seen on wrecks are cylindrical fire-tube boilers, in which heat from the fire is ducted through tubes that run through a boiler full of water. Water-tube boilers work the other way round, with the fire heating tubes of water. They are much quicker to heat up, are more energy-efficient, lighter and able to work at higher pressures.

The disadvantage is that water-tube boilers are more complicated and so expensive to manufacture, and also more expensive to maintain.

The vast majority of fire-tube boilers are found on merchant ships, with water-tube boilers almost exclusively used for warships (notable exceptions are the water-tube boilers used on Liberty ships such as the James Eagan Layne, Wreck Tour 62, April 2004).

The wreck in the area of the boilers is broken down to the keel, though further back the main deck is reasonably intact (9). The engines that were fed steam by the boilers are presumably hidden somewhere below the intact deck.

Continuing aft, on the centre-line of the deck is a wedge-shaped raised section with various pulley blocks littered about it (10). The purpose of these becomes immediately apparent to the port side of the deck, where a minesweeping drone or “fish” rests reasonably intact, though a little rotted in places (11).

Just aft of the minesweeping gear, a depth-charge mortar tube points out at an angle, with a ready supply of depth-charges stacked in a recess in the deck behind it (12).

This recess would also have been the location of the main 105mm gun, evidenced by the pintle and mounts resting across the back of the recess to port (13). The gun itself has fallen to the seabed just off the port side of the hull (14).

The main 105mm gun rests on the seabed on the port side
The main 105mm gun rests on the seabed on the port side

Now at the stern (15), the records we have been able to discover and the configuration of the wreck do not coincide. The hull of the M-343 was just one example of a generic design used by the Kreigsmarine throughout WW2 that went through a number of evolutions.

When the M-343 was launched in December 1941, the configuration was for twin propellers and a single rudder. However, this wreck has twin propellers and twin rudders, a configuration adopted to improve manoeuvrability in mid-1943.

As the M-343 is the only vessel of the series lost in this area, and because it was not lost until June 1944, the identification is most likely accurate. Perhaps the production of the different configurations overlapped, or else it was originally built with just one rudder and later upgraded.

Rounding the stern to the starboard side, a torpedo rests intact on the seabed just off the stern (16). Many of this class of vessel carried deck-mounted torpedo-tubes, one either side of the bow.

Assuming that the torpedo was part of the M-343’s armament and not cargo, the tubes might well have been salvaged for their large content of non-ferrous metals.

Back on the stern deck, a winch (17) is another part of the minesweeping equipment.

Moving further forward along the starboard side of the wreck, just forward of the recess and on the seabed beside the wreck is another gun-mount, complete with gun-shield and machine-guns (18).

Machine guns and gun shield on the starboard side.
Machine-guns and gun-shield on the starboard side.

Next to this is a depth charge and a spigot/cradle assembly (19) used to launch it from one of the mortars on the deck.

The final point of our tour is the starboard boiler (20), considerably broken compared to the port boiler, though in many ways interesting because of this, because it shows the complexity of the water-tube system.

Armament fitted to this class of minesweeper varied tremendously, though what’s certain is that there were more weapons fitted than our tour shows. So any time left before ascending could be put to good use in searching for further guns off the main body of the wreck.


Just eight days after D-Day, three German minesweepers were steaming flat-out to dodge the Royal Navy forces protecting the cross-Channel supply lines to the invasion troops, writes Kendall McDonald.

Once clear, the minesweepers were to take shelter among the Channel Islands before moving on to sweep up newly laid British minefields in the approaches to the German naval base at Brest. While doing this, they were to be under the protection of the E-boat flotillas based on Guernsey.

One of those minesweepers, M-343, was one of 131 M-boats of the 1940 type, built by German yards between 1942 and 1945. She would also become one of the 62 of that type to be sunk during their sweeping in many theatres of the war in the West.

Despite the loss of nearly half of those built, these minesweepers were well designed for their task – 543 tons, 62m long and 9m in the beam, with 2,400hp engines that gave them a maximum speed of 17 knots. But their defence was light – the usual crew of 87 had one 4.1in gun and two AA guns, a 37mm and a 20mm.

Not that their firepower was to be of much use. The three sweepers were spotted by radar off Cap de la Hague as they started to swing in towards the Channel Islands.

Within minutes they were raked by fire from the RN destroyer Ashanti and the Polish-manned destroyer Piorun. At 1.40am on 14 June, direct hits sank the minesweeper M-83. The other two pounded away into the darkness, but the Navy stopped long enough to pick up 24 German survivors. Then they resumed the chase.

At 2.30 they found the M-412 , crippled her with several direct hits, and then finished the running battle by sinking M-343 as she fled south of Jersey. There is no record of any survivors.

Wreck Tour: The M343


GETTING THERE: John Liddiard dived the M-343 from Maureen of Dartmouth. From the end of the M5 continue south on the A38. Turn left on the A384 for Totness, then the A3122 for Dartmouth. In Dartmouth, Maureen picks up from the floating jetty just into the one-way system. Having unloaded, the nearest long-stay car park is the park and ride at the top of the hill, though you might be lucky enough to find a closer space on a side street.

TIDES: With a 10m tidal range, slack is essential and begins 45 minutes before high water or low water St Helier. On spring tides, slack lasts for less than 15 minutes.

HOW TO FIND IT: The charted position is 49 00.943N, 002 14.628W (degrees, minutes and decimals).

DIVING, AIR & ACCOMMODATION : Maureen, skipper Mike Rowley, 01803 835449, visit Deepsea.

QUALIFICATIONS: Suitable for any sport diver, at a depth well-suited to making the most of nitrox.

FURTHER INFORMATION: Admiralty Chart No 3656, Plateau des Minquiers.
Pros: Well-sheltered in bad weather. Slack water is not required.

PROS: A rare opportunity to dive a German warship.

CONS: Strong tides and short slack water.

Thanks to Mike, Penny and Giles Rowley.

Other German surface warship Wreck Tours on Divernet: F2, Karlsruhe, Wahrendorf V209


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