https://www.youtube.com/watch?v=Q4vM2bkvMs4

Operation Ivy Bells was a highly classified Cold War operation conducted by the United States Navy, aimed at eavesdropping on Soviet undersea communications. Launched in the early 1970s, this covert mission was among the most audacious intelligence efforts of the era, involving specially equipped submarines and daring divers to tap into the Soviet communication lines in the Sea of Okhotsk.The operation centered on the use of submarines, particularly the USS Halibut, to covertly place wiretaps on undersea cables that connected the Soviet naval bases on the Kamchatka Peninsula and the Soviet Pacific Fleet headquarters on the mainland. The Sea of Okhotsk was heavily patrolled by Soviet forces and was a restricted area, making the operation both risky and politically sensitive.The U.S. Navy, in collaboration with the National Security Agency (NSA), developed waterproof recording devices that could be attached to the cables to capture the communications passing through them. These devices were designed not to impair the cable’s function, ensuring that the Soviets remained unaware of their existence. Divers from the submarines would undertake the perilous task of installing the devices directly onto the undersea cables, often diving in difficult and freezing conditions.