(FORTUNE Magazine) – It is, without a doubt, the ne plus ultra in cruising. ResidentSea is to Carnival and the Love Boat what Buckingham Palace is to home. Although it hasn't actually been built yet, ResidentSea will be a floating luxury condo building; as the sales pitch exclaims, "travel the world without leaving home."

The ship will be one of the biggest in the world--15% larger than the QEII in terms of gross tonnage. But ResidentSea will have only 250 apartments, ranging from 1,105 to 2,700 square feet, including penthouses and duplexes. Each comes with a private terrace and whirlpool, walk-in closets, a home entertainment center, and three separate lines for phone, fax, and Internet access. Prices range from $1.2 million to $5.4 million and include all furnishings, right down to cutlery and crystal.

From such well-heeled digs, residents can explore the world's great cities at their leisure. The ship will dock in each port for a minimum of three days, and up to three weeks for special events such as the Olympics in Sydney or the Cannes Film Festival. For days at sea, there will be a fitness center, tennis courts, golf, spa, shops, lounges, bars, and seven restaurants. There's even a hanging garden.

In June of this year, ResidentSea's Norway-based owners began their sales and marketing efforts in the U.S. and Europe, as well as through Christie's real estate arm. But it's not exactly a straight condo purchase. Buyers will own not their apartments but rather the exclusive right to use them--a sort of indefinite lease. Another caveat: purchasers must have a minimum net worth of $5 million.

Sales, nevertheless, have been brisk. Says Robert Burnett, president of ResidentSea USA: "If we were a resort development and had sold this number of homes on the golf course before the golf course was even built, it would be considered a home run." According to Burnett, the company has had sales of about $50 million worldwide to date. Points out one Alaska-based buyer: "When you consider that a cabin with a veranda on the QEII would cost $250,000 for three months, this is almost a bargain." Indeed.

--Anne Faircloth