Hydro-Thermokinesis is the elemental power to heat and boil water and all things that contain water.
With this power, merpeople can heat and boil water, from water molecules to the human body. The hand movement for this power is a closing/closed fist. This may symbolize pressure, tension and the amount of heat needed to boil water. The best known mermaid who has this power is Rikki Chadwick. This is the most dangerous ability of the three original powers.