In Tidewater, Md., where a creek hurries to meet a bay, stands a demure white house.

During the off-season, when its owners are enjoying the city, the house sits quietly and unobtrusively, closed up tighter than a rosebud. It protects itself from the elements through walls of closed shutters that still allow the sun to enter the house as grid-shaped patterns of light.

In winter, the house -- as its architect, Hugh Newell Jacobsen, observed -- goes unnoticed by passing fishermen, sightseers, vandals or architectural students. It wraps itself up against inclement weather. Snugly bastioned, it looks simply like a row of four small white houses, each with its own roof, each joined together by three small hyphenlike extensions. But all put together, the house is 2,300 square feet -- the size of many American houses with three bedrooms.

"Closed, it looks like the standard Tidewater houses," says Jacobsen, "with a steep roof, white clapboard and a stair on the side -- Monopoly houses, the sort of house that children draw with two straight sides and a triangle on top. All the materials, except for the glass, are traditional to the area."

The 300-foot driveway is a mixture of gravel and sand. Crushed oyster shells rim the house and take the drips from the stainless-steel gutters. Except in the carpeted bedrooms, the floor is Pennsylvania blue flagstone, which extends out from the house to make a platform.

But when the warm weather arrives, the house blossoms. Its shutters lift up and out and turn into overhanging roofs, exposing the glass walls underneath, opening up the house to the sparkling waterfront scene and transforming the wrapped-up winter home into a pleasure pavilion at water's edge.

The shutters, cut to look like clapboard, are lifted up by ordinary garage-door mechanisms. They fit into a wooden frame and turn the side of the house into a shuttered porch. In their summer position, the shutters work to keep the sun off the tempered and insulated glass walls and to make the house as cool as a glass of iced tea.

The house is entered at the side, between the first and second of the four "houses." The house on the left is the living room. To the right are the remaining three houses: the kitchen and dining area; two bedrooms and two baths; and, at the end of the row, the master bedroom suite.

The entryway to the living room holds a coat closet. The bar is nearby.

The 24-by-24-foot living room is a crystal square. Where the corners come together, glass meets glass, with no seam or structure to block the view. The room is all glass on three sides, an arrangement of 4-by-8-foot glass panels, some fixed, some sliding, so that the living room also can be opened up in summer.

One enters the living room behind the large fireplace. In winter, the fireplace dominates the room, providing a kind of blazing cave fire in the cold weather. It is a manufactured unit with a stack that rises from the mantel to the ceiling, a Breuer Box, as Jacobsen calls it (after the architect Marcel Breuer, who popularized the device).

On the far side of the fireplace in the living room, guests step down into the sunken "conversation circle," set two feet down in the floor. The result is a 10-foot-high ceiling in the center. And from this room, guests are at the perfect eye level, so that when they look out they see the water, first of the swimming pool and then of bay beyond.

JACOBSEN IS HAPPY with the living room plan because it leaves too little space around the circle for people to clutter it up with furniture and spoil the effect.

In winter the cushions in the conversation pit are covered by a fabric of winter-gray tweed and white sailcloth. A stone-colored wool rug warms the area under the Mies van der Rohe glass- topped coffee table. In the summer, the tweed cushion covers zip off in favor of pale blue.

To the right of the entryway is the hall, the spine of the house, which leads first to the dining room and kitchen areas (both with butcher block counters and tables). Two guest bedrooms and baths are on either side of the hall. The double-size master bedroom with its bath is at the end. The attic serves for summer furniture storage.

The tennis court, which is outside the living room, has a blue surface, in complement to the water. The swimming pool has its own changing rooms as well as a summer kitchen; all can be closed down with shutters in the same way as the house.

The project, built two years ago, won an American Institute of Architects Honor Award, Jacobsen's fifth, and was chosen as an Architectural Record House, the 18th for Jacobsen.

Jacobsen designed most of the furniture in the house, selected the all-white Rosenthal china, the Georg Jensen pistol-grip stainless-steel tableware, the Henri Bendel glassware and even the vacuum cleaner.

When the owners drove up to the completed house for the first time, Jacobsen had also mixed the martinis.