Cetacean Telco

There is a horizontal extent of ocean called SOFAR in which — owing to environmental factors — sound waves travel more slowly. Slowly enough, in some cases, to propagate for thousands of miles before they attenuate. During the Cold War, the US built an autonomous acoustical array in the South Pacific to listen through SOFAR for Russian submarines. It’s still down there, in the deep waters, listening. Even more remarkably, it would appear that some species of whales know it’s there and use it to place long distance calls. They swim down and sing into it, to other whales at the same depth miles away. Basically, it’s telecom infrastructure for cetaceans.