HMS Seal (N37) - Loss in Kattegat

Loss in Kattegat

Having been at sea for a year, and suffering some damage from a close scrape with a merchant ship, Seal was due to return to dry-dock at Chatham. However her sister ship HMS Cachalot had been rammed and needed serious attention in the dry-dock. Some repairs to Seal were carried out at Blyth, Northumberland, and she was required to take over Cachalot's minelaying duties. She was assigned to Operation DF 7, a mine-laying mission in the Kattegat between Denmark and Sweden. This was a particularly daunting task, especially for a submarine the size of Seal. Captain Bethall, the commanding officer of the flotilla, failed to persuade Admiral Horton to reconsider his orders.

On 29 April, Seal left Immingham laden with fifty mines. On entering the Skagerrak, she met HMS Narwhal just leaving the area after having stirred up German defences by scoring six hits with six torpedoes. Seal was running at shallow depth to maintain speed and conserve energy, when she was spotted by a German Heinkel He 115 on 4 May at about 02:30 am. She dived to 90 feet (27 m) and was slightly damaged by a bomb. Later that morning, Lonsdale discovered German anti-submarine trawlers searching for them around her target area, and he had to divert to the secondary target area. At about 09:00 am, Seal started to lay down the 50 mines and completed that mission some 45 minutes later.

Seal turned and headed for home, with the trawlers heading after her. Lonsdale took an evasive course, and used the Asdic to identify when the trawlers were stopping to listen. Then, at 3:00 pm, he spotted a patrol of nine German anti-submarine motor torpedo boats heading from a different direction. There were too many hours of daylight left, and the Kattegat was too shallow to allow a submarine as large as Seal to go deep and run for it. Lonsdale evaded detection by following a zig-zag course and at around 6:00 pm settled the submarine in stop-trim at the bottom of the sea. Unknown to the crew, they had entered an uncharted minefield. One of the submarine's hydroplanes caught a mine stay-cable and at about 06:30 pm, the attached mine was swept by the current onto the stern of the boat. There was a huge explosion and Seal was severely damaged.

A painful increase in air pressure indicated that a large amount of water had entered the submarine. The crew's evening meal was catapulted round the mess rooms and the boat tilted bow upwards at about ten degrees. All the watertight doors were quickly sealed and all crew accounted for, after two who had been trapped in the after end of the boat managed to make their way to the control room. To the crew's surprise, the pursuing ships had not noticed the explosion and moved away. After various inspections and repairs, the crew had to wait until 10:30 pm when it was dark enough for an attempt to be made to raise the submarine.

At 10:30 pm, the ballast tanks were "blown" and the main motors started, but the stern stayed firmly stuck on the sea bed. The bow rose at a sharp angle, and the attempt had to be abandoned. By this time, the air quality had deteriorated badly. Pumping carried on and emergency repairs were made to start the pump to blow air into the rear trimming system. For a second attempt to surface, the 11-ton drop keel was released. This meant that the submarine could not submerge again. More high pressure air was used to blow the remaining tanks, but again the attempt was unsuccessful. Carbon-dioxide poisoning was having an accelerating effect on the crew and a third attempt was called for, using the engines and main ballast. This also failed.

At 1:10 am, Lonsdale, a devout Christian, called his crew to prayer and led them in the Lord's Prayer. The crew then responded to his order for them to move as far forward as they could to try to tip the balance, though many fainted or were sick. While thoughts went to using the Davies escape gear, it was realised that it would take several hours to escape by this method and there was a risk of flooding the entire craft before more than a few could escape. The engineers found they could open a salvage-blow and a final attempt was made to raise the submarine. The motors caught fire, but this went out for lack of oxygen. The batteries were nearly empty and the high pressure air exhausted. The engineer realised there was one air pressure group left with a tiny amount of air, which was some way up the companionway. He reached and opened the valve, and the submarine started to move upwards.

Seal surfaced at 1:30 am. After the pressure was released, the fresh air caused blinding headaches to the crew, who had suffered oxygen deprivation. Lonsdale clambered to the bridge, and sighting land, decided to try to make for Swedish waters. The confidential papers were consigned to the sea bed, and the Asdics were destroyed and the pieces thrown overboard. Lonsdale sent a message to the Admiralty: "Am making for the Swedish coast". With the cipher books destroyed, Lonsdale did not receive two replies - "Understood and agreed with. Best of luck" and "Safety of personnel would be your first consideration after destruction of the Asdics". If he had, they would have saved him a considerable amount of anguish over his subsequent decisions. The rudder was damaged and the boat impossible to steer, but it was found that it could be made to go in reverse. Fair progress was made, but mud had entered the lubricating system and the one working engine seized up.

At 02:30, Seal was spotted on the surface and attacked by two German Arado Ar 196s and another Heinkel. Lonsdale on the bridge, under fire, tried to fend them off with the Lewis guns, but these both jammed. With Seal under bombing and gunfire attack from the air, unable to dive and without motive power, some men wounded and no remaining defences, he had no alternative but to surrender. The white messroom table-cloth was hoisted on the mast. Leutnant Schmidt brought his seaplane alongside and required the captain to swim to him. On his 35th birthday, Lonsdale swam to the seaplane, and shortly after, the chief petty officer swam to the other Arado. The crew waited on the submarine for the anti-submarine naval trawler UJ-128, to arrive at 06:30. It was expected that the boat, which was holed and listing, would sink of its own accord, but attempts were made to scuttle her. The German boarding party took the crew off, and the submarine was towed to Frederikshavn.

The mine belt laid by the Seal sank one German freighter (Vogesen, 4241 BRT) and three Swedish ships between 5 May and 5 June for a total tonnage of nearly 7000 BRT.