THIS MONTH'S WRECK TOUR takes us across the Channel again to Normandy. Our target is the wreck of HMRT Sesame, an Assurance-class tug launched in January 1944 and sunk by an E-boat just after D-Day, on 11 June, 1944.
     I have always had a soft spot for a nice tugboat; lots of engineering crammed into a small space, and no empty holds between it all. I dived the Sesame from mv Maureen and Mike Rowley hooked the shot nicely across amidships.
     Getting to the wreck at 20m, the first thing to be seen among an enormous shoal of fish is the Samson post (1). This consists of a pair of pillars and a ring fixed securely into the keel of the tug, to which towing cables could be secured so that the power of the tug could be used without pulling the ship apart.
     The Samson post is just forward of the engine (2), the top of which is just below main deck level. Debris from the ventilation hatch above has fallen in among the crowded bits of engine-room which, together with silt, leaves just the top part of the engine casing visible.
     All Assurance-class tugs were originally built with three-cylinder triple-expansion steam engines, though in post-war civilian use some were re-engined with diesels. The Sesames sister ships Tenacity and Prudent were rebuilt in this way and re-named Rivtow Viking and Rivtow Lion, used for towing rafts of logs in British Columbia.
     In fact the Rivtow Lion has recently been sunk as an artificial reef off Nanaimo on Vancouver Island.
     There is just a small area of deck behind the engine with a storage box, then the steering quadrant (3), flush with the deck and attached to the rudder-post.
     Below the stern, the rudder is turned almost 90Â to starboard, though this angle is not reflected in the position of the steering quadrant above, indicating that something has come loose in the overall assembly. A four-bladed iron propeller is still attached to the shaft, the upper starboard blade being broken (4). At the bottom of the scour, the depth is 24m.
     Moving forward along the starboard side, a three-sided frame (5) sticking up from the banked sand would have been part of a deckhouse covering the boiler.
     Other bits of debris along this side include a plate with an eye above it and then, closer to the bow, a fair amount of debris from the wheelhouse (6).
     As the sand shifts, a small hole may be visible about here.
     The bow itself stands almost 6m clear of a scour to 24m. A simple anchor winch (7) stands above empty hawse pipes. The top of the bow is flush with the forecastle and the gunwales cleared down to main deck level.
     All that remains is a pair of steel eyes to either side of the anchor winch.
     Next back is a large square hatch to the chain-box (8) with pairs of mooring bollards on either side. Then comes the wheelhouse or, more correctly, the place where the wheelhouse would have been (9). There is a scattering of debris across an obvious frame on the deck, with more debris over the starboard side as mentioned earlier.
     Photographs of Assurance-class tugs show considerable superstructure forward of the Samson post, all of which has either now decayed or been swept clear. Even so, it is hard to imagine where the 31 crew would all have fitted on a ship this small.
     Either side of the wheelhouse, tight against the side of the ship, is the steering cable. This runs the length of the ship to the stern, round the steering quadrant, and back along the other side. The ships wheel would have pulled the cable one way or the other, turning the rudder.
     Behind the wheelhouse is the base of a high-pressure water-pump (10). This is quite a common feature on a tug, and could be used for fighting fires or pumping out ships taking on water.
     Last stop before the Samson post again is the boiler (11), a single oil-fired unit that can just be picked out below the covering debris of, presumably, a skylight and funnel.
     Assurance-class tugs are listed as carrying a 3in gun, a 20mm gun and two machine-guns. I could find no sign of these, or even the gun mounts.
     Supporting the D-Day landings as she was, it is unlikely that the Sesame was unarmed, so I can only assume that the armament was all salvaged.

Thanks to Deane Wynne; Mike, Penny and Giles Rowley; Alex Poole and members of Bloxwich Sub-Aqua Club.

The German 5th Flotilla of E-boats, based at Le Havre, was a crack outfit. Its high-speed sweeps of the Channel from the very beginning of the occupation of the French naval base in 1940 brought much grief to Allied shipping, writes Kendall McDonald.

Now, in the dark of the earliest hours of 11 June 1944, the Le Havre E-boats were on the rampage again, this time hunting for vessels bringing in replacements and supplies for the US troops pushing inland from the D-Day beachhead of Omaha.

HMS Sesame, a small, newly-built Admiralty tug and the latest in the Assurance class, just happened to get in the way. She was there with other tugs to seek out and assist any ships in trouble off the Normandy beaches. But she had no time to tow anyone, nor to open up her 1350hp engines, which could push her 157ft length along at 13 knots.

On deck she carried a single 3in anti-aircraft gun, backed by a 20mm Bofors and two machine-guns. She had no time to fire any of the guns at the long dark shapes which roared at her and past her. In seconds the E-boats were gone into the night, with only long white trails of froth to mark their passing. Except, that is, for a torpedo which had struck Sesame in the starboard side amidships, and left a gaping hole.

Though she sank within five minutes, another older Assurance class tug on Normandy assistance patrol, HMS Stormking, managed to pick up some survivors from her crew of 31. Sesame was the fifth and last of Assurance-class tugs sunk during the war.

broken coaming round a hatch in the rear deck

The anchor winch

scour beneath the bow

a shoal of bib obscuring the pump base

GETTING THERE, DIVING, AIR & ACCOMMODATION: John Liddiard dived the Sesame wreck on a trip to Normandy aboard mv Maureen from Dartmouth. Call 01803 835449, www.deepsea.co.uk/boats/ maureen. From the end of the M5, continue south on the A38. Turn left on the A384 for Totnes, then take the A3122. In Dartmouth, Maureen picks up from the floating jetty just into the one-way system. Once you have unloaded, the nearest long-stay car park is the park and ride at the top of the hill. Other liveaboards make Normandy trips from many south coast ports.
TIDES: Slack water is essential and occurs one hour before high water Dover and five hours after high water Dover.
HOW TO FIND IT: The co-ordinates are 49 27.564N, 000 54.720W (degrees, minutes and decimals) datum ED50. There are no transits. The wreck lies east-west..
QUALIFICATIONS: Minimum qualification of a reasonably experienced sports diver. .
FURTHER INFORMATION: Admiralty Chart 2073, Point de Barfleur to Courseulles. D-Day Wrecks of Normandy by Mark James. Janes Fighting Ships of World War Two.
PROS: At an average depth of 22m, the Sesame makes an ideal second dive, with little need for long decompression stops.
CONS: Only really a practical destination from a liveaboard charter or from a trip based in Normandy.