I know I mentioned this before, but I want a way for players to have a finite time they can breathe underwater. Distinct from the DPS from water setting that already exists, as I want it so that players can swim without taking damage, so long as they surface before breath runs out.
As a minigame setting, you can set the time limit, as well as how much DPS a player receives after they run out of breath. Bonus for a swim speed setting, separate from the regular player speed already in the game.