Hissing, burning to touch

My boyfriend just dropped his already smashed iphone into the pool, obviously theres water damage, but since getting it out of the pool its making a hissing sound and burning hot to touch. what can we do? is there a chance it could be dangerous?

UPDATE: the noise has stopped, but it’s still too hot to touch! Its midnight and I don’t know where to put it in case it does explode or catch fire