it is permissible for the husband and wife to bath together in the same place even though he sees her private parts, and she sees his. this is established by a number of authentic hadith, among them:
on the authority of 'aa'ishah (radiallahu anha) who said: "i used to bathe with the prophet from a single container of water which was placed between us such that our hands collided inside it. he used to race me such that i would say: `leave some for me, leave some for me!' she added: `we were in a state of janaba (i.e. the state of having slept together).'"[al-bukharee and muslim].
on the authority of mu'aawiya ibn haida, who said: "i said: `o messenger of allaah, which of our nakedness is allowed, and of which must we beware?' the prophet answered, "guard your nakedness excpet from your wife or those whom your right hand possesses." (so it is permissible for both spouses to look at and touch the body of his or her companion even the private parts). he said: `o messenger of allah, what about if the relatives live together with each other?' the prophet answered : "if you can make sure that no one ever sees your nakedness, then do so." he said: `o messenger of allah, what about when one is alone?' the prophet said: "allah is more deserving of your modesty than are the people"."[ahmad, abu dawood, at-tirmidhee and others: saheeh].