10 January 1924

Sank off Portland following collision with HMS Resolution

HMS L24 was detailed to take part in Exercise GA in January 1924, which was intended to improve submarine tactics in dealing with aircraft, both friendly and hostile. On 10th January HMS Resolution, a 29,000-ton battleship, left Portland bound for the exercise. After several hours at sea a lookout on board the Resolution reported a disturbance on the surface ahead and at 1113 a slight bump was felt. L24 was shortly afterwards reported missing and salvage vessels were dispatched to the area.

Unfortunately night soon fell and the weather the next day prevented any further search and by the 12th all hope of finding survivors had to be given up. The Resolution was checked for evidence of a collision, her chain was found to be fractured at the very bottom and this was taken as evidence of a collision. It is believed that L24 was unaware of the Resolution’s position having carried out a mock attack on another ship and was surfacing when she suddenly became aware of the looming battleship. A crash dive was probably attempted but L24 was unable to avoid the battleship.

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12 November 1925

Sank in English Channel following collision.

On 12th November 1925 M1 sailed from Plymouth to take part in an exercise. Several vessels reported seeing the submarine on the surface during the course of the proceedings and M1 exchanged messages with the minesweeper Newark at 0730. At 1937 M1 dived and never resurfaced.

What happened to the submarine remained a mystery for several days until the Captain of the Swedish collier Vidar made a report of his journey from Cardiff to Stockholm. On entering the English Channel British warships were seen carrying out exercises. The Vidar was continuing on her way when at 0745 a heavy blow rocked her. The Captain put this down to bombs being used in the exercise as his ship was still perfectly watertight, and proceeded on his way without communicating with the warships. Only on reaching the Kiel Canal on 16th November did he read about the ongoing search for the submarine. Three days later it was possible for divers to inspect the hull of the Vidar where it was found the stem had been bent and several rivets were missing, indicating a collision with an underwater object. Traces of paint on the colliers stem were later found to be identical to that of M1. The search for M1 continued for a month until on 2nd December the Admiralty announced that the search was to be discontinued as nothing had been found.

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9 August 1926

Sank at Devonport - surface trimming with hatches open

On Monday 9th August 1926 HMS H29 lay alongside No.2 Basin in Devonport Dockyard. She had recently completed a refit and it was necessary to test the torpedo tube mechanisms. In order to do so the submarine was required to be "trimmed down". As the submarine began to trim several men came rushing on deck. H29’s stern began to sink low in the water and attempts to shut the aft hatch were thwarted by a 4-inch pipe passing through it. Water began to rush through the hatch before the pipe could be removed. H29 sank in under 2 minutes.

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9 July 1929

Sank off Pembrokeshire Coast following collision with HMS L12

On Tuesday 9th July 1929 HMS L12 was at sea with an Officer Training Class; at the same time H47 was on independent exercises in the Irish Sea. At 0800 both submarines were off the Pembrokeshire coast with L12 ahead of H47. L12 suddenly altered course to starboard. H47 at once went full astern and to collision stations. The two submarines crashed together with L21’s bow penetrating about 2 feet. In only 15 seconds H47 began to sink. L12 also began to take in water but her crew managed to control the flood.

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HMS Poseidon

9 June 1931

Sank north of Wei Hai Wei following collision with SS Yuta

On 9th July 1931 HMS Poseidon was exercising 20 miles north of her home base of Wei Hai Wei when the steamer Yuta was spotted some distance away. Despite excellent visibility the two vessels collided and the submarine sank within two minutes.

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26 January 1932

Sank off Portland whilst surfacing

At 9 o’clock on the morning of 26th January 1932 HMS M2 left Portland to take part in routine exercises. At 1011 she signalled her intention to dive at 1030. This was the last communication with the submarine. The loss of radio communication did not cause any consternation until M2 failed to return to port as expected at 1615. Search vessels were dispatched but there was no sign of the submarine or her crew. No explanation could be found for her loss until the Admiralty received a report from the captain of the coaster Tynesider which reported seeing a submarine diving stern first off Portland. This had caused the Captain some anxiety but he thought he saw the same submarine a short time later. M2’s exact position remained a mystery for a week until the Destroyer Torrid picked up sonar sounds that indicated a sunken submarine; divers confirmed this to be M2 lying with her stern in the sand at a depth of 90ft

Two bodies were recovered from the wreck during the next week. A number of attempts were made to raise the vessel but all failed.

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HMS Thetis

1 June 1939

Sank in Liverpool Bay during trials

On 1st June 1939 HMS Thetis left Birkenhead for Liverpool Bay to conduct her final diving trials, accompanied by the tug Grebecock. As well as her normal compliment of 59 men she was carrying technical observers from Cammel Laird and other naval personnel, a total of 103 men. At 1340 pm Thetis signalled her intention to dive and that she would be submerged for 3 hours. As the submarine began her dive it became clear that there was a trimming problem as she would not submerge, despite the ballast and auxiliary tanks being full and 50 extra men on board. Such problems were not uncommon in new submarines but it was necessary to check that Thetis had taken in sufficient water to submerge. Part of the check entailed examination of the six bow torpedo tubes to ensure that tubes 5 and 6 contained the 100 gallons expected. The Torpedo Officer first checked tubes 1 to 4 and all were dry. On opening the test-cock to tube 5 it appeared the tube was dry. As the tube was opened water cascaded into the submarine.

In the control room ballast tanks were blown, but too much water had entered the submarine and she became wedged in the mud at a depth of 150 feet at an angle of 45 degrees. An Indicator Buoy was released and smoke candle fired. By 1600 Grebecock was becoming concerned for the safety of Thetis and radioed Gosport. A search was immediately instigated. Next morning HMS Brazen found the Thetis with her stern clear of the water, and dropped charges to mark her arrival to any survivors still trapped in the submarine. The survivors began their escape two men appeared on the surface followed by two more. These were the only men to escape from Thetis. Attempts were made to cut holes through the pressure hull. A wire that had been placed around her stern finally parted and the submarine slipped beneath the waves.

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HMS Oxley

10 September 1939

Torpedoed in error off Obrestad, Norway by HMS Triton

HM Submarines Oxley and Triton were patrolling off Norway on 10th September 1939 and had been in regular contact when Triton spotted an unidentified submarine off the coast of Norway. Believing it might be Oxley a number of signals of recognition were flashed by Triton. No reply was forthcoming and after several challenges Triton fired two torpedoes that struck the submarine and sent her to the seabed. Triton closed in on the area and found three survivors. A Board of Enquiry found that Oxley was some way out of position and that Triton had acted correctly and was not culpable for the sinking.

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HMS Undine

7 January 1940

Sunk south west of Heligoland by German A/S trawlers

HMS Undine was on her fourth war patrol in January 1940 when her asdic failed due to a leak. At 0940 on 7th January, Undine sighted what was thought to be three trawlers 20 miles west of Heligoland; but were in fact German minesweepers. Undine unsuccessfully attacked the leading vessel; minutes later there was a large explosion followed by others as the minesweepers opened fire. Undine was at 50 feet and proceeding blind due to the loss of asdic. After 5 minutes of no further attacks Undine raised her periscope as she did so an explosion shook the submarine, blowing her upwards and rendering the hydroplanes useless. Without the use of the hydroplanes escape would have been impossible and the order to abandon ship was give. Whilst the crew entered the water, to be picked up by the minesweepers, demolition charges were set and the submarine scuttled.

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HMS Seahorse

7 January 1940

Possibly sunk by German A/S craft

On 26th December 1939 HMS Seahorse sailed from Rosyth for patrol off the east coast of Denmark. Four days later she shifted position to the entrance of the Elbe. She did not return on her due date of 9th January 1940. It was first thought that she had been mined but German records, examined after the war, suggest she was the victim of the German First Minesweeper Flotilla which reported a sustained depth charge attack on an unidentified submarine on 7th January 1940.

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