"The Bloop" mysterious ocean sound louder than any creature

This was like the Wow! signal of the deep. Louder than any creature by far. Not man made. Good speculation about the source but does anyone really know for? Research it and see what you think. Personally I think even if it were Cthulhu we'd call it a glacier =) "Julia" coming up . . . Image and sound credit NOAA Source: http://oceanexplorer.noaa.gov/explorations/sound01/background/seasounds/media/bloop.html