We only did a cruise in Tahiti on Princess, but based on my reading beforehand, technically Tahiti is pretty topless friendly but as far as straight c/o, not so much. And there is no way to make a blanket statement about 'over water bungalows', you would have to consult the particular resort you are staying in. Depending on the resort, the individual bungalows could be very private from each other, but the pictures of most resorts I have seen is that they are all lined up right next to each other. The traditional wisdom that I have always heard regarding nudity in Tahiti is that you can get someone to take you to a deserted motu and you can be nude there.

If you decide to go, Tahiti is fabulously beautiful. Enjoy..