True, there is Jimmy Hoffa, Osama Bin Laden, a ton from the Neptune society and so forth.
I should have said microphones. Don’t know if they are still in use but I found this article
Scientists Object As Navy Retires Ocean Listening System
June 12, 1994|By New York Times News Service.
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The Navy, facing increasingly tight budgets, is shutting down most of a $16 billion system that spied on enemy ships and submarines for decades by monitoring their undersea sounds. But scientists are fighting to save as much of the network as possible for environmental research and other civilian uses.
In a post-Cold War windfall, scientists and federal experts have been using the system to track whales, spy on illegal fishing, monitor earthquakes and volcanoes at sea and look for shifts in ocean temperature that could portend climatic trouble.
“It’s ridiculous to throw away a $16 billion investment when it’s got so many uses for mankind,” said Adm. James Watkins, a former chief of naval operations who is now president of the Joint Oceanographic Institutions, a Washington-based consortium of universities and research groups that study the seas.
The Sound Surveillance System, or Sosus, was used during the Cold War exclusively to track the ships and submarines of America’s foes.
Started in secrecy in the mid-1950s, it spans the globe with a network of more than 1,000 underwater microphones grouped in arrays and tied to Navy shore stations by some 30,000 miles of undersea cables. It can track undersea sounds over hundreds and sometimes thousands of miles of ocean.
With military budgets shrinking fast, the Navy has quietly begun cutting maintenance, closing shore stations and preparing to dismantle or mothball about 80 percent of the undersea arrays, Navy officials say.