The HMS Thetis Sinking

Send us Fan MailA submarine is already a coffin-shaped idea, but HMS Thetis proves how fast “routine” can become irreversible. We’re telling the story of the 1939 HMS Thetis disaster in Liverpool Bay, where a brand-new British Royal Navy T Class submarine goes down during dive trials and turns a simple systems check into a deadly cascade.We walk through what Thetis is, how diesel electric submarines operate, and why early sea trials matter so much. Then everything hinges on details that sound harmless until they aren’t: enamel paint blocking a torpedo tube test cock, confusing bow cap indicators, and a single inner door opened to the sea. The result is immediate flooding, a steep nose-down impact on the seabed, and a packed hull with far less breathable air than anyone planned for.Above the surface, the rescue effort stumbles in ways that are hard to believe: the escort tug drifting off station, communications delays, a search starting miles away, and precious hours slipping by even after the stern breaks the surface. Below, we track the human cost as oxygen drops, carbon dioxide rises, and hypoxia and hypercapnia strip away the ability to think clearly. We also get into the Davis escape gear attempts, the choices made topside about preserving the hull, and the long tail of lawsuits, Admiralty findings, and the safety recommendations meant to prevent another submarine sinking like this.If you’re fascinated by naval history, submarine safety, and how small procedural failures become catastrophe, subscribe, share the show with a friend, and leave a rating or review.Facebook: historyisadisasterInstagram: historysadisasteremail: [email protected] thank you to Lunarfall Audio for producing and doing all the heavy lifting on audio editing since April 13, 2025, the Murder of Christopher Meyer episode https://lunarfallaudio.com/