Events
On This Day - December 30
| 1940 | Umpire (N82) | Launched |
| 1940 | Undaunted (N55) | Completed |
| 1940 | Unbroken (P42) | Laid Down |
| 1940 | Unison (P43) | Laid Down |
| 1941 | Thorn (N11) | HMS Thorn torpedoes and sinks the German tanker Campina about 5 nautical miles west off Cape Dukato. |
| 1941 | Ultor (P53) | Laid Down |
| 1941 | P52 | Laid Down |
| 1942 | Simoom (P225) | Completed |
| 1944 | Terrapin (P323) | HMS Terrapin sinks two Japanese sailing vessels with gunfire in the Malacca Strait. |
| 1944 | Trenchant (P331) | HMS Trenchant sinks a Japanese sailing vessel with gunfire in the Malacca Strait. |
| 1944 | Tapir (P335) | Completed |
| 1954 | Shrimp (X52) | Launched |
