The Soviet Navy Built 1 Titanium Submarine That Could Dive 3,350 Feet. It Sank in 1989 With 2 Nuclear Warheads Still Aboard.

She was the only one of her kind: a titanium submarine built to dive below the reach of NATO's weapons, and she set a depth record that still stands. On her first operational patrol she caught fire, and the emergency blow that brought her up fed the flames the air that finished her.