During the cold war, the US and the Soviet navy had been encountering strange sounds from the dept of ocean off the coast of Norway. Both superpowers put huge efforts into hiding their submarines, and into detecting the other side’s submarines, and as a result, there were huge advances in the technology required for listening for any signals from the ocean depths. As a result, the two navies heard some unusual things.
From the mid-1970s onwards, Soviet submarine crews started to report strange sounds in the waters of the Arctic and North Atlantic oceans. They were driven crazy by “Quackers,” inexplicable and unidentified underwater objects that moved underwater at a speed of 200 kilometers (125 miles) an hour.
NATO assumed that it was Soviet submarines that made the noises until finally one of the commanders of the Soviet Navy asked the Norwegians to catch at least one “Quacker” for him at all costs and promised to reward the Norwegians for it.
In 1991, the US submarine detection system picked up two unidentified signals at once in the Pacific Ocean. Scientists nicknamed one of them “Upsweep,” and the other “Whistle.” Neither one nor the other could be identified. “Upsweep appeared every spring and autumn, and its source was in the middle of the ocean, and Whistle was heard only once.”
In 1997, the US military and ocean explorers were alarmed by a strange signal, which was nicknamed “Bloop.” The U.S. National Oceanic and Atmospheric Administration (NOAA) recorded it roughly triangulated to a remote point in the south Pacific Ocean west off the southern tip of South America, and the sound was detected several times by the Equatorial Pacific Ocean autonomous hydrophone array.
The Bloop was heard at a range of over 5,000 kilometers, and is several times louder than the blue whale, the loudest known underwater animal sound. It was so strange that oceanologists began to joke that it was Cthulhu, a fictional cosmic entity created by writer H. P. Lovecraft. Moreover, scientists could not guess what it was. It seemed like the sound was made by a gigantic living creature.