This is actually (spoilers for terrible movie Scales: Mermaids Are Real) the climax of the movie Scales. Mermaids can control water and their blood heals people in that movie, so hunters are trying to get their blood and then one guy tries a last ditch bad guy move and the main character pulls all the water out of his body and he horrifically melts.

Kind of made me side with the hunters at that point it’s a horrifying power.