In 1997, the U.S. National Oceanic and Atmospheric Administration (NOAA) recorded an ultra-low frequency sound in the deep Pacific, dubbed “The Bloop.” Detected by multiple hydrophones thousands of kilometres apart, it was one of the loudest underwater noises ever captured, sparking theories of a colossal unknown sea creature near the southern tip of South America. While NOAA later suggested shifting ice as a likely cause, the sheer power and mystery of the sound continue to fuel cryptid speculation and documentaries about monsters of the deep.