Reading comprehension clearly isn't everyone's friend.

To all those guys who are saying they bathed/showered with their fathers and it was no problem: that means nothing in this thread.

The OP is talking about bathing with his four year old DAUGHTER.

The only posts about sharing a bath or shower with a parent that is relevant in this thread are those by women who showered with their fathers growing up or boys showering with their mothers growing up.

At a certain age (like right about now) that becomes inappropriate. In fact at the age of four this girl ought to be able to bathe herself (supervised) so why get into the tub with her?

When I was five, I was bathing on my own. No supervision. Surely a four year old can do the same (with supervision if necessary).

Perhaps the OP should ask his daughter whether SHE wants him in the tub (or even in the room) so she has the opportunity to let it be know if she's feeling uncomfortable about the situation.

He's not in some third world country where water is scarce.

Another problem with bathing with a child of the opposite sex at that age is that kids like to mention things at the most inopportune time as well as embellish things as well. My aunt was being hassled by Child Protective Services for years because teachers or neighbors would overhear what her daughter said to a friend. My aunt never did anything wrong but small children love to tell stories and so something that might be totally innocent can be easily misconstrued. Especially if the child embellishes as my cousin did. For example, my cousin when she was about seven just would not stop eating and thus kept putting on weight. So my aunt got a lock for the refrigerator to stop her from helping herself 24/7. Well my cousin tells her friend about locks and whatnot but then, in hearing distance of a teacher, embellishes the story and makes it seem that my aunt is locking her in the basement and not feeding her! Needless to say, Child Protect Services came knocking and my aunt went through hell proving to them that her children were not being abused in any way.

What happens if the OP's daughter says something about daddy touching her vagina or him having a big cock (which some may think means erect and then you have people wondering why you're sporting an erection in front of your daughter)?

Again, just because you're not bathing with your old-enough-to-bathe-on-their-own child doesn't mean you're implying that nudity is evil. It's about setting boundaries and, yes, allowing them to do things for themselves rather than babying them forever.