He [Chupeta] became the first narco-trafficker to use narco-submarines. Drug Lords: The Takedown s1e7: Cocaine CEO, agent, National Geographic 2023
During the Cold War both the United States and the Soviet Union deployed submarines with ballistic missiles. Spy Ops VIII: Project Azorian
They were looking for an object [sunken sub] three miles below the surface. ibid. man in the know