Just when you thought it was safe to go back in the water - well, it is, actually.

A mystery triggered this week by the bizarre discovery of the carcass of a 3-foot-long shark in a freshwater river in northern Austria ended Saturday when a man confessed he had put it there as a joke.

The prankster, an apprentice chef working at a hotel in the province of Upper Austria, told the newspaper Oesterreich that he put the dead shark in the river Voeckla after it began to smell while he was thawing it out for a buffet.

Its discovery on the riverbank earlier this week caused a stir, with Austrian experts hard-pressed to explain what a shark was doing in a freshwater stream in the landlocked alpine country.

The chef, whose name was not released, told the newspaper that several regular customers were in on the joke and had placed bets on how long they could keep the controversy going.