What if you could sail the seven seas and never leave your house? Imagine having a home in dozens of countries! If this intrigues you, consider The World of ResidenSea. The World is a 44,000-ton Norwegian-built, 12-story luxury ship that has a crew of 250, about 200 residents and guests, and 165 one-to-three room apartments and studios. The cost of a home on The World ranges from around $850,000 to $6.3 million (not counting maintenance fees), and the ship has all the amenities of a gated community – including a Country Club! The World had its maiden cruise in March 2002, and travels the globe, stopping for a night or two in ports from A to Z – Athens, Barcelona, the Canary Islands – you get the idea. (Contact www.aboardtheworld.com or 305-264-9090 for more info)

With the successful concept of a ship as a floating home established, several additional in-the-water communities are in the planning stages. Four Seasons has commissioned a 96-apartment, 43,000-ton ship offering full or fractional ownership, with the level of services and amenities you\’d expect from a Four Seasons property. The launch of the Four Seasons Ocean Residences, which will travel around the globe, is planned for 2007. Tentative prices are $4.1 million for a full residence and $400,000 for a fractional ownership. (Contact www.oceanresidences.com or 305-438-7447 for more info)

The Magellan is the brainchild of Randall B. Jackson, a Phoenix real estate developer (Jackson\’s inspiration for this luxury vessel occurred while cruising through the straits of Magellan with his family). Still in the pre-construction phase, plans for the Magellan include a 70,000-ton ship boasting not only the usual amenities, but also an observatory (staffed by an astronomer), and a marina. The two hundred homes on 15 decks begin at $1.9 million for full ownership, and $160,000 for fractional ownership. Of course, don\’t forget the monthly assessments (beginning at $8,000). The ship, slated to launch in 2008, will stop at more than 150 ports per year. (Contact www.residentialcruiseline.com or 480-497-8833)

Another residential ship with a target launch of 2008 is the Orphalese (named after the city in The Prophet by Kahil Gibran). Two hundred fully-furnished homes will be available, ranging in size from 1,000 to 4,000 square feet, priced from $1.8 to $10 million, with monthly fees beginning at $2,500. There will be an additional 265 staterooms for regular cruisers. You can enjoy the 80,000 square-foot mall in between visiting 200 ports per year – the itinerary of the Orphalese is event-driven rather than destination-driven. (Contact www.theorphalese.com or 888-287-7447 for more info)

The most ambitious project under consideration is the Freedom Ship, which, as its website states, “is actually nothing more than a big barge.” Although not off the ground (er, water?), CEO Norman Nixon envisions a slow-Moving city that circumnavigates the globe once every three years, spending 30% of the time moving, and 70% of the time offshore from major cities. Not only would the 4,500 foot-long Freedom Ship have residential, commercial, and hotel properties onboard, there would also be schools, parks, an airport, and medical facilities to serve its total population of 100,000. (Contact www.freedomship.com or 941-539-6824 for more info.)

Finally, how about “Assisted Living at Sea”? Lee Lindquist and Robert Golub published an article in the Journal of the American Geriatrics Society (November 2004), concluding that for those who needed some assistance with food preparation, house-cleaning, and access to medical care, it could be just as cost-effective, and provide a better quality of life, to live on a cruise ship as to live in an assisted-living facility. A hypothetical 80-year old woman, for example would pay $228,075 in an assisted-living facility compared to $230,497 on a cruise ship over a 20-year time span. Food for thought!

So, if you like the idea of traveling the world without ever leaving home, and you have the considerable funds to pay for this type of lifestyle, you may want to consider a seagoing city.

Jan Cullinane is the co-author of The New Retirement: The Ultimate Guide to the Rest of Your Life (Rodale, 2007). She gives seminars on the (primarily) non-financial aspects of retirement through her company, "Retirement Living from A to Z."