| Navy | The Royal Navy |
| Type | Submarine |
| Class | Porpoise |
| Pennant | 37 M |
| Built by | Chatham Dockyard (Chatham, U.K.) |
| Ordered | 1 Jul 1936 |
| Laid down | 9 Dec 1936 |
| Launched | 27 Sep 1938 |
| Commissioned | 24 May 1939 |
| Lost | 5 May 1940 |
| History | Captured by the Germans on 5 May 1940. |
Commands listed for HMS Seal (37 M)
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| Commander | From | To | |
| 1 | Lt.Cdr. Rupert Philip Lonsdale, RN | 1 Nov 1938 | 5 May 1940 |
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Noteable events involving Seal include:
4 May 1940
29th April 1940: Sailed for operation DF7 with 50 mines from Immingham, to lay minefield near the Swedish island of Vinga in the Kattegat, across German transport route to Norway. Lt. Cdr. R.P. Lonsdale, RN. While evading surface ASW craft, hit mine and forced to sit on bottom until dark. Surfaced eventually but almost uncontrollable. Aft compartments flooded. Tried to make for Sweden. One engine started but stern damage caused the boat to circle. At 0250 4th May 40 attacked by German He-115 aircraft from Aalborg, Denmark. Spotted by German Ar-196 seaplane, which attacked. Joined by second 'Arado'. Unable to dive, with crew suffering from CO2 poisoning, Seal put up a fight but the Lewis gun jammed. At 0630 the UJ-128 arrived on the scene. The crew surrendered, expecting the boat to sink, but it stayed afloat. 60 crew taken prisoner. Boat towed to Frederikshavn, and on 11 May to Kiel. Commissioned by Germany as UB in Nov 1940, commanded by Fregkpt. Bruno Mahn, a WWI veteran of UB-21. UB had limited value for Germany except for training and propaganda purposes. One benefit was the analysis of British torpedoes, leading to improved detonators for the unreliable German torpedoes. Decommissioned in July 1941 and scuttled in Heikendorf Bay, Kiel, (54.22N, 10.11E) 3 May 1945. The wreck was later raised and broken up.
5 May 1940
The small Swedish vessel Aimy hits a mine and sinks. The mine was laid by the British submarine HMS Seal (Lt.Cdr. R.P. Lonsdale, RN) in the Kattegat in position 57?33'N, 11?35'E on 4 May 1940.
(see map)
6 May 1940
The German merchant Vogesen (4241 GRT) hits a mine and sinks. The mine was laid by the British submarine HMS Seal (Lt.Cdr. R.P. Lonsdale, RN) in the Kattegat in position 57?33'N, 11?35'E on 4 May 1940.
(see map)
28 May 1940
The Swedish merchant Torsten (1206 GRT) hits a mine and sinks. The mine was laid by the British submarine HMS Seal (Lt.Cdr. R.P. Lonsdale, RN) in the Kattegat in position 57?33'N, 11?35'E on 4 May 1940. (see map)
5 Jun 1940
The Swedish merchant Skandia (1248 GRT) hits a mine and sinks. The mine was laid by the British submarine HMS Seal (Lt.Cdr. R.P. Lonsdale, RN) in the Kattegat in position 57?33'N, 11?35'E on 4 May 1940. (see map)