Bathing a baby??

We took Mason out of his bath seat a couple of days ago so he can have freedom in the tub.
But he's just TOO crazy and hard to handle. He goes wild in there, splashing, standing up, crawling. He's bumped his head a couple of times already too. We don't want to hold him a lot when he's in the tub, because it would just be like he's in his seat. But we don't want him to hurt himself.
So what are we going to need to do with him? Soon he's going to be too big for the seat and I'm worried he's going to really hurt himself because he's just so crazy in the tub.