When Columbus made his way across the Atlantic, his largest ship was the 85-foot Santa Maria, carrying a crew of 40, while the Pinta, 69 feet long, held 27, and the 55-foot Nina, 21. Today, some of the privately owned boats plying the Chesapeake are as large as Columbus's three ships, yet their owners boast that they can accomodate only four, six, maybe eight.

Apparently, boat design has changed. Rather than provide only the bare necessities, naval architects have sought conspicuous comfort. Otherwise, why call it a pleasure boat?

Not so long ago a cozy interior meant laboriously varnished woodwork, berth made for munchkins and galleys considered plush if they had an ice box. Now boat designers have more on their minds than seaworthiness. Any boat dealer can tell you that prospective customers spend little time admiring keel shapes and rigging. They head for the rooms below.

Among the most impressively designed homes on the waters of the Chesapeake Bay this summer is the 67-foot Burger motor vessel in the photographs at right. This custom-built ship was one of only four made by its Wisconsin manufacturer in 1975. It is owned by Annapolis real estate developer Wilfred T. Azar. Yours for a cool $895,000 (down from $1.1million), the boat will do about 13 knots and has an all-aluminum hull that is lightweight and therefore fuel-efficient (in this size and price range one is often talking about gallons per minute, but this Burger uses about 40 gallons of diesel fuel per hour at full throttle). The pilot house is a technologist's dream -- three depth finders, radar with a 45-mile radius, a massive compass, two radio telephones plus a powerful single-side-band radio.

Tom Norton of Interyacht, the firm brokering the vessel, says, "The Burger is the kind of boat that someone who doesn't know much about yachts might characterize as a boat built without regard to cost -- but to a real yachtsman, it's a boat designed to give a rich man his money's worth."

The money's worth includes comfortable quarters for six quests and two crew members, a well-outfitted galley, showers, a bath, a washer and dryer, air conditioning, stereo, tape deck and, of course, two color televisions -- all the necessities of a lush summer home without the nagging problem of mowing the lawn.

For those more modest tastes and pocketbooks, there is the Bertram 58 on these pages, owned by a Bethesda developer. Luxuriously appointed, the deep-V hull and efficiently designed bridge make it a great fishing machine.

The master stateroom feature a king-sized bed, wall coverings and a faucet that delivers chilled water. The stateroom amidships sleeps two; there is a forward cabin as well. In a pinch, the saloon, a living room, can be converted to additional sleeping quarters. The Bertram is what is called a "stock boat," though that is like saying the luxury apartments at the Watergate are prefabs.

The owner of the boat, called the See Bird, prefers to be anonymous. His captain, Jim Raleigh, maintains the boat and pilots the owner and his friends on long fishing trips.The boat is moored in Fort Lauderdale every winter.

"The owner is an old Navy man, like myself," says the soft-spoken captain. "He can run the boat as well as I can and does."

Another fine ready-made boat with custom touches is a 52-foot Irwin called the Canadienne, a motorsailor owned by Wanda and David Fischer of Springfield, Va. The Fischers' boat is lined with teak below deck. It's about 15-feet 5-inches at its widest, and all its appointments give one the feeling of being aboard a much larger vessel. The Fischers are customizing the interior so that as soon as their last child finishes school -- in about five years -- they can live aboard the boat all year.

The efficiently designed galley boasts a gimbled oven that allows cooking while under way, a freezer, a refrigerator, an icemaker, a double sink, even a microwave oven.