As long as fishermen's tales have been told, there is always a recurring one.
It speaks of the Behemoth.
Seemingly sentient, this creature does not feed on humans, but finds delight in torturing them in the most gruesome ways possible.
After being swallowed whole, you enter a tunnel filled with extremely foul and noxious acid. You will feel a larger dread than you could have ever imagined. Unspeakable horrors fill up your mind until you can think of nothing else.
Once you are on the verge of killing yourself, the Behemoth expels you, always near other humans. If you do not succeed in killing these humans, you will most probably be taken to a mental asylum to spend the rest of your life.
If you do succeed in killing them, you will regain your sanity. But at what price?