Vodnická čertovina.

When something flashes across the pond dam in the early evening, it could be the gamekeeper Čeřínek, or the poacher Kopýtko and the tailor Nitka, or... could it be Pepík and Franta? A water sprite, no, water sprites don't exist, only superstitious old women and the poor fish warden, who is a little scared of guarding the carp in the tower, believe in them. At least that's what Kopýtko and Nitka think as they plunder the pond so that their mischievous wives can show off. And what if they manage to catch a colossal fish, a carp bigger than anyone has ever seen before? Immediately, a plan emerges in their greedy minds to pass the carp off as a water sprite, display it in pubs, and make a fortune.