This isn't a fish but in 1999, i think it was, or 1997. Maybe. Anyway, that's irrelevant.
But a massive noise was heard the was so incredibly loud it was recorded in two different places thousands of kilometres away. Scientists say that it sounds like it was a noise made by an animal, but no animal known to man is large enough to produce such a loud sound. Even giant squid that have occasionally washed up on beaches are no where near large enough. They call this noise the 'Bloop.' I find it really fascinating and kind of creepy too, I don't really know why.