In the 1960s, the US Navy set up an array of underwater microphones around the world to track Soviet submarines. Most of the sounds detected emanate from obvious sources like ships, whales and earthquakes, while some of the more baffling ones can be explained by underwater volcanic activity, ocean currents and the like. However, some signals remain a mystery. Perhaps the most prominent one of those is Bloop.
In the summer of 1997, the Equatorial Pacific Ocean autonomous hydrophone array recorded an extremely powerful ultra-low frequency sound that ”rises rapidly in frequency over about one minute and was of sufficient amplitude to be heard on multiple sensors, at a range of over 5,000 km”. In addition, the nature of the noise made scientists almost certain it came from a living being. The problem was that it was far too powerful to have been made by any creature known on Earth. You can listen to Bloop on NOAA’s website.
The deep, open ocean remains, for all intents and purposes, completely unexplored. It is not much of a stretch of the imagination to think that vast, undiscovered creatures could exist down there. Maybe that’s what Bloop is – sounds of a creature of the deep.