Soviet submarine K-219

The [Yankee-I class submarine]? K-219 (SSBN) sank in the Atlantic, 680 miles northeast of Bermuda, on October 6, 1986, after suffering an explosion and fire. The seal in a missile hatch cover failed, allowing seawater to leak into the missile tube and react with residue from the missile's liquid fuel.

Three sailors were killed outright and a fourth, an enlisted seaman, died after successfully securing the nuclear reactor by hand, trapped in the engine compartment. The submarine was intentionally scuttled by the captain when attempts to tow it failed. The seaman was postumously awarded the Red Star for his bravery.