The ability to manipulate water,or,if the hydrokinetic person is powerful enough,control the very umidity on bodies to achieve a variety of effects,like drying the water inside them to dehydrate them,make the water violently tear apart the body in question,or create water out of the thin air,and cover he's/her's body with a water barrier.even though no one in the marvel continuity has ever achieved this,it's presumed that very powerful hydrokinetic persons can do it. Just to give an example of hydrokinetic: Hydro-Man.