A Russian submarine, the K-278 Komsomolets, sank at a depth of 5,500 feet, resulting in a tragic loss. The submarine, which was armed with nuclear-tipped torpedoes, has been leaking radioactive isotopes for years, with some reports indicating levels 800,000 times above normal. The incident, which occurred decades ago, remains a significant event in naval history, with the submarine's nuclear missiles still unrecovered.