While you were barbecuing in your backyard this long holiday weekend, America's elite were likely setting sail on huge, tricked-out yachts with plasma TVs and built-in Jacuzzis.

Twenty-first century Rat Pack pals George Clooney, Brad Pitt and Matt Damon chartered a yacht to keep themselves amused while filming heist caper “Ocean's Twelve.”

Tiger Woods set off on his pleasure craft, Privacy, in 2004 after his Barbados wedding to model Elin Nordegren.

Mariah Carey has been noted for her penchant for renting a yacht more than 170 feet long with massive staterooms and a Jacuzzi. And even the rich and famous covet an invite to a party on Sean "Diddy" Colmes' waterborne palace.

Photo Essay: Yachts

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But celebrities may have to make room out on the waves as a flotilla of new American yachtsmen and women fill the oceans.

“Last year our total units sold was around 4,000 units, and we saw same-store sales growth of 21 percent,” said Bill McGill, CEO of MarineMax of Clearwater, Fla., which includes celebrities such as Woods as clients.

"If you go back to 1998, when we went public, we were $290 million in revenues, and through consistent internal growth and sales, we've hit just south of $1 billion last September and will be north of $1 billion this year, with 85 locations in the U.S."

And the biggest-selling yachts are the largest ones.

“The larger boats in particular, over 80 feet, have seen a backlog that's growing year by year,” said McGill. “It's grown faster than any other segment, and for us, it's really about boats over about 50 feet.

“Yacht” is a broad term, but generally is taken to mean any waterborne pleasure or racing craft, be it power or sail.

In common usage, it's a term usually reserved for high-end or luxurious craft, with boats over 80 feet or so long often referred to as “megayachts” and those above 120 or 150 feet sometimes earning the moniker “super megayachts” or something equally superlative-laden.

A sporting yacht between 40 and 65 feet might range between $450,000 and $650,000, but for the megayachts, “the sky's the limit,” according to PricewaterhouseCoopers' principal Allison Shipley, who specializes in clients with yachts.

McGill, for example, offers a 112-foot boat for $10 million.

And cruising yachts are getting larger, decked out with more and more amenities, such as several plasma-screen TVs, stereo equipment, hot tubs and the kind of doodads that wouldn't look out of place in Richie Rich's summer home.

Not only are yachts bigger than they used to be, they're also more hooked up.

"It used to be when I first got into the business in 1973 you might have a TV, and some boats had generators and boom box stereos, that kind of thing.

"Now you have navigation system where you can paint pictures on the bottom as you go along, not one TV but three flat-screen TVs, sophisticated integrated stereo systems just like in their homes, so the boats are pretty well self-sufficient,” McGill said.

Spectacular recent growth is also being seen among some companies that manage the boats while they're in dock, so that owners and groups who share ownership can enjoy the benefits of the sailing life without the humdrum hassles of maintaining a vessel.

“At the end of 2005, we had 23 boats in the water; today we have been projecting well over 60 by the end of this year,” said Carlton Morris, managing director of The Cruising Club USA, based in Frisco, Texas. “We're opening markets at a pretty fast rate.”

There are lots of reasons why more and more people are buying yachts in a time when people are straining just to take the car to work.

Some say that competitions like the now-televised America's Cup or the Louis Vuitton Cup whip up seagoing enthusiasm.

Shipley pointed out that some people take advantage of the fact that a yacht can be treated as a second home for tax purposes (as long as it has eating and sleeping facilities; a bathroom, strangely enough, isn't required).

David Slikkers, CEO of S2 Yachts of Holland, Mich., said the terrorist attacks of Sept. 11, 2001, were a cause for the upswing in family-oriented yachting.

Many, like McGill, point to the fact that Baby Boomers are spending more and more discretionary dollars on recreation.

And it certainly doesn't hurt that America's ultrarich are growing richer than ever before.

“People say, I want this thing called my leisure time to be the very best for myself and my family,” McGill said. “High-net-worth individuals and ultra-high-net-worth individuals have more money than they ever had before, and that's what's fueling our growth.

"Baby Boomers with discretionary dollars, they say, 'My leisure time is very important, I work hard, work longer hours than any other nation, and I want an escape from this hectic life that I live.'"

But while Mariah may spend her yachting time in her Jacuzzi, simpler can be better, according to Tom Berton and Chris Van Nes, owner and captain, respectively, of the Shearwater, an 82-foot, 1920s-era schooner yacht that sails New York Harbor.

“At night we play dice, play guitar, sing songs,” Van Nes said as the pinewood-and-teak Shearwater pulled past a gigantic fiberglass yacht that looked like a cross between a wedding cake and the space shuttle.

“You look at those boats and you see the people sitting inside on the couch watching a plasma-screen TV. I could do that at my girlfriend's house.”