After some Serious Contemplation, I'm gonna def go with this being permanent. And just to let you know so it's all kosher: As much as I still like my stupid blowfish idea, Jesse will develop webbed hands/fingers and feet/toes, and purple gills open up on the sides of his neck and the sides of his ribcage when in water. It's an ability he has to learn to control, so showers and such things will at first have Jesse turning into a manfish with bright purple eyes automatically. (Eventually when he learns to control it, tho, he'll be able to "switch on" his manfish abilities at will in water.) When he's not a manfish, the gills seal up and look like very faint light purplish scars that would only attract people's attention if their attention was pointed to it/if they looked closely enough and noticed. The webbing retracts when he's not a manfish; his hands and feet look normal when he is his normal self.