“One of my players was playing as an earth elemental cleric. They were sailing to some far away island when everybody was dicking around, and they knocked said cleric into the ocean. Of course he didn’t float and sank straight to the bottom (couldn’t drown either, technically).
It took the players ~3 sessions of underwater themed adventures to finally get him rescued. Because he had spent so much time under immense pressure on the ocean floor, he came out as a lava elemental, and now he cant set foot in wooden buildings, and nobody can touch him without taking burn damage. If the players wind up in a particularly cold environment, they just crowd around him for warmth now, which means they don’t need to build campfires anymore. Unfortunately, he is incredibly bright at night, and has a -7 stealth modifier.”