"I forgot you can breath underwater"
we had been playing a fantasy age of sail kind of game using a system that the GM cooked up. The party took a job delivering a box, which earned us an enemy in the form of a half elf sorcerer who was significantly higher level than us. he had been hounding us through our last several ports of call, with the party just barely escaping with their lives from the last several encounters. The party being a murderous gnome, a human sailor, a human weather witch, a human wizard, a human mercenary, and a large frog man shipwright.
So we leave a doctor's office in totally not fantasy Venice. Standing on the opposite shore of the canal is the sorcerer. He immediately starts casting spells, poison cloud, and a telekinetic attack. The frog man takes a running leap and lands in the canal. the rest of the party scatter away from the poison, one of them fires a crossbow, and the gnome passes out (he was already injured, which is why we were at the doctor). 2nd turn the sorcerer TK tosses the guy with the crossbow. he is then very surprised when a the frog man leaps out of the water grabs the sorcerer and plunges back into the water. The sorcerer struggles, but he can't cast without speaking, and the frog man is super humanly strong, so breaking out of a bearhug is just not happening. The GM asks for a check for the frogman to hold his breath. "I don't need to" "huh" "I've got water breathing" "... Oh. I forgot about that." "yeah. also contact poison skin" The rest of the combat consists of the elf trying to escape, and the frogman sitting there at the bottom of the canal until the sorcerer loses consciousness. When the elf loses consciousness his magic armor panic teleports him away. The frog swims back to the surface to tell the rest of the party what happened.
He stopped putting boss fights near water after that.