"I can't heat the entire lake," Antonin replied with a laugh. "Well, I probably could with a little work, but the merfolk would most likely get upset. Not something one does lightly."
"Warming charms it will have to be for you poor witches and wizards that have problems with heat and cold. I am offering doses of the mermish charm so you don't have to use your own bubblehead spell or gillyweed."