Ayesha R.A. reported: Rasulullah (SAW) and I bathed in one utensil, and the mubarak hair of Rasulullah (SAW) was longer than those that reached the ear lobes, and were less than those that reached the shoulders". (It means that they were not very long nor were they short, but of a medium length).
It is not clear from this hadith if both bathed in a state of undress. Ayesha R.A. herself says: 'I did not see the private parts of Sayyidina Rasulullah (SAW), nor did he see my private parts'. Also the using of water from the same utensil cannot prove this. There are many ways both could have bathed from the same utensil and yet not see the private parts of one another.
From this hadith we also learn of the bathing together of husband and wife. The ulama are unanimous in accepting Imaam Nawawi's saying that this is jaa'iz (permissible). Another method is that the husband bathes first and the wife bathes after him with the remaining water. This is also unanimously accepted by all. The third method is the opposite where the wife bathes first then the husband bathes with the remaining water. This method is accepted by the Hanafis, Shaafi'ees and the Maalikis. The Hunbalis says it is not permissible, but if the husband is present and both bath together, then it is permissible. The pros and cons of this subject are very lengthy, therefore they have been omitted here. This subject have been mentioned briefly in Arabic commentary. Since a reputed Imaam opposes this, and this has also been mentioned in the hadith, it will therefore to better to abstain from it.