UC42 Cork

The dive

UC-42 was a Type UC II minelaying U-boat of the Flanders Flotilla, built in 1915 and lost off Cork on her sixth patrol. German records give the date of loss as 10 September 1917, the day she was due back from patrol. The wreck was not found until 31 October, when the Royal Navy torpedo-boat TB055 followed an oil slick and depth-charged it; dockyard divers went down on 2 November and identified her from a marking plate on the conning tower, reporting the stern destroyed and hatches open. Everyone on board died, a complement reported as 26 men under Oberleutnant Hans Albrecht Muller, and as 27 in total. The most likely explanation for the loss is that one of her own mines detonated, or that she struck the seabed while laying them. She was lost again for ninety-three years until Irish divers relocated her in November 2010 and identified her from a serial number stamped on a propeller.

She sits on her port side at around 28 m, bow pointing north, on a 45 m hull that is largely recognisable. John Liddiard's wreck tour for DIVER magazine runs the dive from amidships, where a large section of cladding stands above the starboard side, forward along the keel to an external bow torpedo tube lying in the silt and the remains of the port-bow hydroplane, then aft along a line of six vertical mine-laying tubes. Several of those tubes still hold the rotting remains of their mines, with the explosive filling visible inside the broken casings. Behind them are a ventilator, an open hatch, the conical mount where the 8.8 cm deck gun used to sit, and the torn-off conning tower lying alongside the hull with its periscope and hatch. Aft again are the diesel air intakes, the base of the radio mast, a hole through which the batteries are visible, the aft hydroplane and rudder linkage, and a single stern torpedo tube. The highest point of the wreck is the starboard propeller shaft and propeller, mostly under plumose anemones, with the cone polished bare by divers' hands; the team who found her in 2010 left a plaque on the shaft.

This is a war grave and a protected wreck, and that is the most important thing on the page. Ireland protects every wreck over a hundred years old automatically under the National Monuments Acts, and the National Monuments Service requires a Dive Licence under section 3(5) of the National Monuments (Amendment) Act 1987 for dives, surveys and archaeological activity at wrecks and protected underwater cultural heritage sites. Nothing may be lifted. Germany retains an interest in her as a war grave: when a propeller lying about 15 m from the hull was raised on 17 June 2024, it was done by six divers from Blackwater Sub Aqua Club with Mizen Archaeology, supported by the National Monuments Service, the National Museum of Ireland and the German Embassy, and the object went straight to conservation. Do not penetrate the hull and do not touch the mine tubes.

The fish life recorded around this pin is what you would expect on a deep Irish wreck: conger, pollack, bib and poor cod, ballan and goldsinny wrasse, leopard-spotted goby and topknot, with brown crab, edible urchin, spiny and seven-armed starfish and large solitary sea squirts on the structure itself. Bottlenose and common dolphins, minke and fin whales are all recorded in the wider approaches.

• Six vertical mine-laying tubes, some with mine remains still inside
• Conning tower torn off and lying alongside the hull with its periscope
• Starboard propeller under plumose anemones, the cone polished bare and stamped UC42
• A 2010 memorial plaque on the propeller shaft

Conditions

A boat dive of a few kilometres from Kinsale or the Cork Harbour slips, dived on or near slack water. The wreck is compact enough to tour in one dive. Nothing in the sources read here gives a visibility figure for the site.

On current: DIVER's wreck tour puts slack water at high and low water Cobh and says slack is only really necessary on spring tides. Published depths disagree and the difference matters for gas planning: Wikipedia gives 27 m, the DIVER wreck tour 28 m, and RTE reported the 2024 propeller recovery as being made from 30 m. Plan for the deeper figure. The position also disagrees with our pin: the wreck tour publishes GPS 51 45.077 N, 008 12.909 W, about 2.4 km north-west of the catalogue coordinates.

Dives & underwater footage