My GSD enjoys lying down in the bathtub?

I have a young female GSD who loves water and will hop in the bathtub and just lie down in there for a while. It's pretty funny because all my dogs have hated it when I try to get them in the bathtub for a bath, but she hops right in without thinking twice. Anyone else here have a dog or know a dog who likes the bathtub. It doesn't matter if it's cold outside she still hops in, so I don't think she's doing it to stay cool. She loves water and tries to lick it up, could that be a reason? She also is safe from our other GSD in there since our other female is afraid to go in the bathroom. Maybe it's a safe spot for her? Just brainstorming. Any ideas why she does this???