"It was to have been a quiet evening at home. Home is the Busted Flush, a 52-foot barge-type houseboat, Slip F-18, Bahia Mar, Lauderdale."

So begins The Deep Blue Goodbye, the first in Sarasota author John D. MacDonald's series of mystery novels featuring Travis McGee, the knight-errant hero whose base of operations is the boat he won in a poker game. When the book was published in 1964, and for the next 21 years until MacDonald released The Lonely Silver Rain just before his death in 1986, a 52-foot boat seemed like quite a grand vessel. It was surely enough to help ol' Trav woo his share of women and entertain friends in decent fashion.

But despite the brass plaque at the Bahia Mar Marina honoring the fictional boat, and Slip F-18's designation as one of Florida's official "Literary Landmarks," the marina's other erstwhile residents might not think too highly of a puny 52-footer should it tie off next to their yachts these days.

"Let's put it this way: I have clients who buy 80-foot tenders for their yachts," says yacht salesman Peter Croke. "For them, a 52-foot boat is barely a dinghy."

Welcome to the rarified world of mega-yachts, floating palaces that are now topping out at 400-plus feet, where on-board amenities include such indulgences as basketball courts, helicopter pads and personal submarines. Ownership of the truly big yachts is the purview of folks like billionaire Microsoft co-founder Paul Allen (the 414-foot Octopus), Oracle Corp. chief Larry Ellison (the 452-foot Rising Sun) and certain oil gazillionaires (one Saudi royal family member is expected to launch the 526-foot Platinum in 2006); but Southwest Florida residents also own their fair share of big yachts, some among the largest in the world.

Father-and-son real estate developers Raymond and Scott Lutgert, of Naples, last year launched the 164-foot Andale, from Italian shipbuilder Codacasa. It has an elevator to transport guests from deck to deck and, when the Lutgerts aren't entertaining on it, charters for $230,000 a week. Naples residents Lee and Penny Anderson lay claim to Katherine, a 177-footer that regularly cruises the Mediterranean. And Sarasota automobile dealer Vern Buchanan is proud master of the Entrepreneur, a 110-foot craft launched in 2004, which comes with a surround-sound theater, a hot tub and a 32-foot center console boat that can be towed behind and used for water skiing, scuba diving or sport fishing.

While folks who call Florida's Gulf coast home are among the most ardent buyers of big yachts, that doesn't necessarily translate into seeing them out on our waters. "I'd say the Naples-Sarasota area easily ranks as one of the highest per capita yacht ownership areas in the U.S.," says Jim Gilbert, publishing director of Showboats International, a slick monthly magazine based in Fort Lauderdale and dedicated to the mega-yacht lifestyle. "It's hard to tell, of course, because when you get yachts of this size people don't exactly park them in their back yards."

There are several reasons for that. For one, the Gulf's shoals and shallow waters make for tricky navigating. Plus, few marinas along Florida's west coast are equipped to handle yachts longer than 140 feet.

Vern Buchanan bought his first boat, a 16-footer, when he was 18.

"I've been going upwards ever since. Had a 54-footer, then a 70-footer and now the 110-footer," says Buchanan. "I'm happy with it for the foreseeable future. But will I get an even bigger one? Never say never."

One reason Buchanan bought Entrepreneur was because the yacht's six-foot draft was suitable to Gulf waters. "Lots of the big boats don't make it to the Gulf, but I couldn't imagine not having mine here, at least part of the year," says Buchanan. "Sarasota is just such a mecca for yachting."

The big yachts tend to stick to a standard circuit: the Caribbean and Bahamas in the winter, the Mediterranean in the summer, with stops in Fort Lauderdale along the way. But then, yachts of this size can go just about anywhere they want to, provided there's plenty of deep water. A yacht like the Lutgerts' 164-footer typically has a cruising range of at least 5,000 miles, making it easy enough to plan a round-the-world cruise. Just have plenty of cash on hand when that 31,000-gallon gas tank hits empty.

Not only is Fort Lauderdale home to the Bahia Mar Marina and other notable big-yacht docks, it's also the site each fall of the Fort Lauderdale International Boat Show, the largest in-water boat show in the world. When the big yachts are put up for sale, this is where you'll find them. Fort Lauderdale is also home to a sizeable population of "boat people," whether trained crew and captains for the big boats or the skilled mechanics and craftspeople who keep them running smoothly and looking good.

"It's safe to say that virtually every big yacht of distinction at one time or another passes through Fort Lauderdale, simply because it has one of the largest concentrations of skilled boat craftsmen in the world," says Bob Saxon of Campers & Nicholson, Inc., one of the world's top yacht brokerage and charter management firms.

Still, Saxon and others in the industry are awed by the ever-increasing size of yachts, which are generally defined as boats longer than 85 feet. "But anymore we refer to boats in the 85- to 100-foot range as 'starter yachts,'" says Saxon. "That shows you how crazy the scene has gotten as the boats get bigger and bigger. Just five or six years ago, you could feel pretty special if you had a 100-foot yacht. These days that marker is 200 feet. You go to Monaco in the summer or, say, St. Martin in the winter, and they are just wall-to-wall with 200- and 300-foot yachts. It's mind-boggling."

Indeed, Showboats International, which tracks such things, recently reported that there were more than 250 so-called "starter yachts" scheduled for 2005. That's almost double the number ordered as recently as 2001, when 139 were launched. And industry insiders say there are probably more than 50 yachts of more than 200 feet now under construction, a process that could take anywhere from three to five years.

Considered against other luxury purchases-jewelry, fancy cars, private planes, multiple vacation homes-yachts are surely the most indulgent, conspicuous and hardest to justify in terms of making an investment that will hold its value. Beyond the purchase price-figure at least $10 million for something guaranteed to draw attention (Larry Ellison's Octopus is said to have cost $250 million)-upkeep alone can cost millions of dollars a year. Most owners seldom use their yachts more than a month or so a year but must still pay a crew to keep them ready to go.

"Yachts are like racehorses," says Saxon. "It's not good to let them sit." That's why about 60 percent of all yacht owners put their vessels in charter service. It's not a money-making proposition so much as it is a way to keep the yacht in good working order and, with luck, recoup some of the costs.

And it's not as if the mega-yacht owners can entertain big crowds on their boats. Even the 300-foot-plus yachts have a legal capacity of only 12 guests plus crew; the same goes for many 100-foot yachts. That's because they must abide by international Safety of Lives at Sea (SOLAS) regulations, which require vessels carrying more than 12 passengers to follow much stricter safety and construction guidelines, essentially the same rules and specifications followed by big cruise ships.

So with all these caveats, what's the appeal of the mega-yacht?

"It's the private-island fantasy," says Showboat International's Gilbert. "It's self-contained luxury, secure and safe. And you can take it just about anywhere in the world."

It's also about exclusivity, a way for the ultra-wealthy to separate themselves from those who are merely rich.

"Yachts have always been about status," says broker Croke, who's with Fort Lauderdale-based Merle Wood and Associates, which specializes in yachts of 120 feet and more. "Not only are the yachts getting bigger, but the playthings associated with them are becoming fancier. Used to be you could have a yacht and not pay a great deal of attention to your tenders, as long as you had one. Not anymore. These days, if you have a 300-foot yacht and you take it, say, to Monaco, then you want a 100-foot chase boat to accompany it. That way when you and your friends want to bop off to St. Tropez for the day, you can hop on the chase boat, which will get you there in a hurry, rather than crank up the yacht, which might only go 17 knots. Everything just keeps getting bigger and better, and faster and more costly."

Indeed, the market for mega-yachts seems to be so strong that the only limiting factor, beyond where to keep them, is where to build them. All of the big yachts these days come from shipbuilding yards in Europe, primarily Germany, Holland, France and Italy. Shipbuilders in the United States haven't developed the capacity to go much beyond the 200-foot range. The largest yacht ever built in the U.S. is a 204-footer from a Seattle shipyard. One of Florida's leading yacht builders, Tampa-based Lazzara Yachts, has seen its offerings increase in size over the years from 68 feet to 80 feet to 106 feet. In 2004, Lazzara introduced its first 110-footer, with formal dining for 10, a sky lounge with a 42-inch plasma TV, and 16-cylinder engines that can push the craft at speeds up to 30 knots.

"U.S. builders create some beautiful vessels, but the capacity for the increased size didn't develop over the years, simply because the dollar was strong against the currencies in Germany and Holland and other places," says Croke. "That might change now, what with the euro so strong and people having to pay what amounts to a 30-percent premium on the cost of building a yacht. But really, with the people who can afford these things, even that 30 percent is small change."