Our boats are designed to run as quiet as it is right here in this room. As a matter of fact, the hum you hear from my computer would be the loudest sound you would hear on our boat. I'm very touchy about that," says Stanley Bey on a June morning in his Rumson, N.J., home.

A half-dozen suitcases sit in the entryway at the Bey home, packed for a trip to JFK International for a flight to Barcelona, Spain, later in the day. At Port Vell, Barcelona, Bey and his wife Peggy would board their 125-foot yacht, Perle Bleue, valued at between $28 million and $31 million, for a two-and-a-half week trip on the Mediterranean to Monaco in the south of France.

On June 29, Prince Albert of Monaco presided over ceremonies honoring the world's best boats of 2007, including the Perle Bleue, named ShowBoats International's best full displacement motor yacht under 50 meters.

Bey is one of about 3,000 people in the world who own boats 85 feet (about 25.9 meters) and longer. Silicon Valley mogul Tom Perkins says his sailboat yacht, The Maltese Falcon, is the world's biggest privately owned sailboat, at 88 meters (compared with Perle Bleue's 37.95 meters), with an estimated value of more than $200 million. These large craft are commonly called mega- or super-yachts.

"A luxury yacht is one in which the client's specific needs and requirements are met. This could be in terms of luxurious fitting to specific cruising requirements," says Ron Cleveringa, vice president of sales and marketing at Burger Boat Company in Manitowoc, Wis. "At Burger, how the client will use the vessel dictates how it is designed and built."

Luxurious fittings are limited only by an owner's imagination and wealth: Boat builder Lurssen in Bremen, Germany recently constructed a 224-foot yacht called Kismet with solid honey onyx columns flanking a bathing pool. Hakvoort in Holland has designed one with custom-loomed Lacey-Champion carpeting.

The big boats offer a floating five-star hotel experience with features such as a fully equipped gym/spa; an indoor dining room for 16; satellite TV and DVD and a stereo-CD in all staterooms; Wi-Fi and small-antenna satellite VSATs for Internet access; game rooms, water toys and his-and-hers heads (that means bathrooms on land). At the highest end, the safety features include steel and aluminum construction; multiple bulkheads for safety in case of collision; two bottoms; and fire sprinklers in every room.

Insurance brokers are more specific in their definition of a mega-yacht. "We define them on the insurance side as having a value of over a million dollars and/or being 60 feet in length. But personally, the true mega-yacht to me is a 70-plus footer with a value of $2.5 million on up-way, way up," says Brian K. DeSousa, president of Bay Marine Yacht Insurance in Rumson, N.J.

"Right now, we are seeing larger and larger vessels in this industry. At the present time our average length is 137 feet," Cleveringa says.

Jim Perry, a Miami maritime lawyer, has a client who's building a 432-foot yacht, which, he says, "Almost takes on the definition of being a ship."