Hot water
Hot water[1] (also described as gelatin[2] or ooze[3]) is a toxic, green-colored liquid that appears in Super Mario Sunshine, exclusively during the final boss fight against Bowser and Bowser Jr. at the top of Corona Mountain. During the entire boss fight, both Bowser and Bowser Jr. are found soaking in hot water in a giant floating hot tub.
During the battle, Bowser sometimes ground-pounds the hot tub to splash the hot water on Mario and damage him. There appears to be an unlimited amount of water in the hot tub; when Bowser tilts the tub, most of it falls out, but the supply is immediately replenished. After Mario ground-pounds all five sections that branch off from the hot tub, the entire hot tub tips over, and all of the water falls out of it into Corona Mountain. The large Shine Sprite that was trapped in the water is also set free.