The phenomenon known as 'The Bloop' is quite possibly one of my favorite of the great, unsolved mysteries of the world. It is such a simple thing, a mere sound, but so large it was that several different sensors thousands of miles apart were able to record it. So essentially, in the summer of 1997, a sound was registered, a loud sound and it was traced to the location of 50 degrees S 100 Degrees W, roughly off of the west coast of South America. Each time it occurred, it rose in frequency for about roughly 60 seconds on an ultra low frequency. Heard at normal speed, it sounds like nothing. At least nothing that human ears can discern. However, when sped up by the National Oceanic Atmospheric Administration to 16 times its normal speed, it sounds like a bubble rising in the water.
Supposedly, the profile of said sound matches that of a living creature. The only problem being that according to scientists who have studied said noise have concluded that any creature able to make such a noise would have to be larger than any creature as of yet known to man or science. Creepy.
Giant Squids have for the most part been discounted as traditionally there sounds are produced through gas-filled sacs and no known species posses a sac large enough to transmit sounds through water that can be heard upwards of three thousand miles away. Again though, no known species. Would it be foolish to assume that humans have successfully and completely cataloged our massive oceans. Indeed. And I don't think that anyone could make an argument otherwise. And therefore, is it not possible that such a creature capable of such massive noise could have escaped our technological nets? Not quite as certain, but still, it is a possibility.
Fiction has grabbed a hold of 'The Bloop' in its own special way. My favorite of such things was it's utilization in the viral campaign for the monster film Cloverfield. But the ones who have truly latched onto it in the most glorious and fanatical of ways are the fans of H.P Lovecraft and his demonic creation, Cthulu. Fans have noted that the coordinates of mystery's approximate location match that of R'lyeh, the sunken city where Cthulu triumphantly makes his appearance in the short story "The Call Of Cthulu." It is more than enough proof for them that, Cthulu is indeed alive and well and it was he who made the sound.
But to the great dismay of all who are attracted to such phenomena, 'The Bloop' has not been heard since it's initial but multiple occurrences in 1997. As such, there has been no truly concrete study of the mystery despite enrapturing even those in the legitimate scientific community. And unless 'The Bloop' arises again, it is likely to stay a mystery.
For those wishing to make their own opinions on the matter, this website has audio files of varying quality and speed for listeners to enjoy.