Showering with small children

Another post I just read reminded me of a question I have had.

When is it okay for adults to shower with children? And when does it stop being okay?

I have no problem with children being naked or teaching them anatomy. And you can stop right now if your answer uses the words "sexualizing children."

But, for instance, my SIL has asked my husband in the past if he would be okay with letting her small son shower with him.

I remember showering with my mother when I was a kid and it stuck in my memory and made me confused. I don't want to do anything to confuse (or endanger) my kid. I think I was disturbed enough that I would say it's not a good idea.

But on the other hand, I know my niece has taken a bath with her grandma too and I can't say it's wrong, per say.

What do you think?