[@Zaphander]

PS: Actually, I realized something else while looking over your CS again. You can't use your quirk with normal items/clothing. No one in the entire MHA universe can, that's why Hero/Villain gear exists. I'll have to ask that you take that part out of his Quirk's description since it's not consistent with the rest of the whole series.

Along with choosing what other kind of limit you would like to put on your character's quirk to limit it's duration. Either a stamina one (so that he can do it only for a maximum amount of time before getting exhausted, which will vary depending on the circumstances so it's better to already mention how much he can endure under maximum exertion), or a limit based on how much he can hold his breath since he won't be able to breath while being rock. Or any other kind of limit you can think of, as long as he can't "sit on the bottom of the ocean forever with transformed".

He [i]needs[/i] a limit, is what I'm saying.