But there is one stark difference. Passengers on the white behemoth of a ship, which can carry 2,974 passengers, will enjoy those facilities naked.

The ship's expected nude sailing - the trip is 70 percent booked - underscores the vitality of the US nude tourism industry, which the American Association for Nude Recreation says brings in around US$440 million a year, up about 10 percent in the last decade.

Nude tourism isn't a new concept: Tiemann started booking cruises two decades ago with a ship of 600 people and the American Association for Nude Recreation celebrated its 80th anniversary last year.

Smaller nude cruises have visited the Greek Islands, Croatia and the Italian and French Rivieras in addition to more conservative locales such as Egypt - though travellers were clothed when they toured the pyramids.

Nudists, who say they are not about forcing nudism on others, emphasize the nudist lifestyle is simply about enjoying oneself without the social or physical burden of clothing in a non-sexual, family-friendly environment of like-minded people.

Nude tourism appears to be growing in popularity. A survey of US households with income of $50,000 or more last year showed that 17 percent of respondents saw a visit to a nude or clothing-optional resort as extremely or very desirable.

Those figures were up from 12 percent a year earlier, according to the Portrait of the American Travellers Survey of 2,539 households by the Ypartnership/Harrison group.

Nudists also appear to be seeking out a higher-end experience far removed from the more affordable rustic tent camping and family-oriented sing-alongs by the campfire of previous generations, experts say.

The owner of another nudist resort, DeAnza Springs Resort in Southern California, said he had bought much of the tiny town of Jacumba on whose outskirts his resort sits and was in the process of renovating the hot springs and facilities there.

Owner Dave Landman said he did not want to turn the town into a nudist colony, but possibly an artists' community that nudists would see as friendly.

On cruises and at nudist resorts, where a strict code of conduct applies, owners occasionally have to deal with guests who came with faulty expectations, although several said that this was an increasingly rare experience.

Overt sexual activity is barred at resorts that fall under the American Association for Nude Recreation's banner, and sexualized clothing or accessories are not considered appropriate.