Help me find the story about the creature pulled from the sea by fishermen 150 or 200 years ago or more.

The creature was chained and taken to church, eventually was released, and the story went that it came back onec or twice before leaving forever.

What is your original source?

No, that's not it Anglosaxon, but interesting nonetheless.

My source was I read it somewhere on the internet, I think whilst researching bigfoots in UK. If I find it again I'll update this thread.

The story was that a fisherman brought it into his boat in his net, it was not a fish but a creature, and it must have breathed air because they took it to the sherriff cell and locked it up, at some point it was decided to take it to church to see if it held any reverence of god.

The fisherman took pity on it and arranged to smuggle it back to the sea and release it. (might be confusing the story with fiction here. see below)
It helped the fiserman fish for a short time before dissappearing for good so the story went.

It has been adapted into a radio play story which was played on radio 4. I heard it shortly after reading about it on the net, and instantly recognised the origin of the story when I heard the play.

Last week (or so) the play was repeated on radio 4 and sparked my curiosity to read the story of the original again. I thought people here would know about it. So I asked.

Will we are at it. If any one has anything on the seacreature found in japan/china. They thought it was a big fish then didn't conceder it a fish.