AFAIK sound is still the only way to detect submarines underwater. Also
"A humpback whale singing in the Caribbean, for example, can be heard by a fellow whale off the west coast of Ireland more than 4,000 miles away. Eighty-foot-long fin whales — second only in size to the blue whale — can make low-frequency moaning sounds beyond the range of human hearing that also travel thousands of miles." [ https://www.dailymail.co.uk/sciencetech/article-5337987/How-whale-singing-heard-4-000-miles-away.html ]
Biting the hand that feeds IT
