Baby penis

Okay so I’m a FTM and I have a boy. My husband and I decided not to circumcise our son. I noticed that when my son is in the bath tub his penis shrinks to almost nothing- is this normal?? Sometimes during diaper changes he gets small erections and his penis is bigger but during baths or sometimes throughout the day, it’s seriously nothing. It just looks like his foreskin sitting on top of his balls. Sorry this is so TMI but I’m a FTM to a little boy, not sure what to expect. :)