Events
On This Day - January 21
| 1905 | A7 | Launched |
| 1907 | C6 | Completed |
| 1908 | C15 | Launched |
| 1918 | H49 | Laid Down |
| 1940 | Seal (N37) | HMS Seal departed Rosyth for her 6th war patrol. She was to patrol in the North Sea. |
| 1943 | Sahib (P212) | HMS Sahib torpedoes and sinks the German submarine U-301 in the Mediterranean west of Bonifacio. There was only 1 survivor from U-301. |
| 1943 | Tigris (N63) | HMS Tigris torpedoes and sinks the Italian merchant Citta di Genova in the Strait of Otranto about 25 nautical miles west of Saseno Island |
| 1943 | Unrivalled (P45) | HMS Unrivalled sinks the Italian sailing vessels Margherita and Ardito with gunfire and scuttling charges about 5 nautical miles north-east of Kuriat, Tunisia. |
| 1954 | USS Nautilus | The first nuclear submarine, USS Nautilus (SSN-571) was launched. After shattering the traditional bottle of champagne across the bow of the USS Nautilus, First Lady Mamie Eisenhower and others gathered at the Electric Boat Yard of General Dynamics Corporation in Groton, Connecticut and watched as the world's first nuclear-powered submarine slipped into the Thames River. |
| 1956 | Artemis (P449) | Was in collision with a motor trawler in the Channel off the Isle of Wight while on exercises. Artemis sustained no damage and carried on. |
