Originally posted by squashplayer1:

Haha, but was a serious question.

So it is a bug? Or do I have to drain the water in this well somehow?

practically, you can't do much.

1. You can to shoot him with the bow
2. You can build a cage floor above water and keep him as a zoo exponate

Draining water isn't possible - there is no liquid flow mechanics for global water level, only for tar