Whenever the weather is good and it is a sea day you will find anywhere from one to more than a dozen people taking advantage of this option.Not all on the topless deck are topless, it is an option and not a requirement. My wife and I have been there once or twice and she will not doff her top, we were there as it was a nice quite uncrowded place to read and relax.
Of the cruise ships sailing in this market, only Carnival has an area set aside for topless sunbathing. On other ships you will sometimes see women with the top undone to avoid a tan line on their back, but, I have not observed any topless sunbathing on Celebrity, Princess, Norwegian or even on Windjammer. You will definately see topless sunbathing in the historically French ports such as Martinique and the French side of St Martin on the beaches.
I've never seen anyone do this in my five cruises.
Mary Lou Scanlon
NCL Pride of America April 24, 2010
NCL Epic February 12, 2011
RCCL Allure of the Seas - September 18, 2011
Celebrity Eclipse - February 11, 2012:
RCCL Navigator OTS - February 9, 2013
On our last cruise, Carnival Triumph last January, there were probably 10 - 25 topless women on the appropriate deck during sea days. There were also women who kept their tops on, and men in thong bikinis. We always sunned on the topless deck, as there are no children allowed - much quieter than the pool area. It was easy to find a deck lounge chair, and it was windier, thus cooler, than down on the pool deck. For the most part, it was a very quiet, relaxing area, with only a few gawkers.