Hydro-Man, Fluid Felon (SPM-033) - Marvel's Spider-Man

Whenever you cast a blue spell, if Hydro-Man is a creature, he gets +1/+1 until end of turn.

At the beginning of your end step, untap Hydro-Man. Until your next turn, he becomes a land and gains "T: Add U." (He's not a creature during that time.)