Situated just steps from the beach in Southampton, New York, this modern cedar-shingled house was originally intended as a summer vacation getaway—until its new owners decided to turn it into an inviting retreat for year-round living, relaxing, and entertaining. “We wanted the decor to give context to the location, but not feel like a ‘beach house,’” notes Marea Clark, the San Francisco–based decorator who was enlisted to oversee the renovation. Her goal: to imbue the house with a stronger sense of character and create a connection with the pristine nature preserve that surrounds it.

“The floor plan was really the starting point,” says Clark, who envisioned the home as a series of intimate zones for reading and relaxation. Guests pass through a covered porch to access the entry, which sets the tone for the home’s quietly coastal character. A settee beneath a wall of antique fish prints invites guests to take off their shoes, while a round table is paired with braided straw stools. Graphic curtains in a black-and-white print—a sort of modern take on a fish motif—contrast with the simple wood-paneled walls. “We didn’t want this house to feel too serious,” notes the designer.

Architect Stephen Whalen extended and enclosed an existing porch to create a relaxed dining and family room, which was a game-changer, as the couple had been eating their meals perched on stools at the kitchen island. The adjacent sitting room-slash-lounge beckons with sleek midcentury touches. Conviviality is key, with a plush sea-colored sofa, a pair of curvy vintage chairs by Giulia Veronesi, and a caned sideboard that serves as a bar. An old-school turntable enhances the Mad Men vibe.

Perhaps counterintuitively, Clark painted the new addition’s walls black and installed ebonized wood floors, creating a dark, cozy envelope that highlights the lush green views outside the window-wrapped walls. Subtly nautical touches like handwoven dining chairs and a V-groove wood ceiling nod to the feeling of being on a ship. “We didn’t want the space to feel cavernous,” says Clark, who stained the ceilings a warm honey color. “We wanted the addition feel like it was always a part of the home.”

In contrast to the entertaining-focused newer rooms, the living room is all about downtime. Clark mixed light and heavy fabrics—silk-cotton ikat, wool, shearling—to make the room feel cozy even when the weather begins to cool. Limewashed inset panels painted a warm gray give the space an appealing depth.

Upstairs, the primary bedroom is all bliss, with a peaceful beachy palette punctuated with black windows and a modern canopy bed, and graphic sea urchin photography. Simple blackout roman shades were a must with the strong sun, says Clark, who forewent any additional window treatments—“we didn’t want anything more obstructing the view,” she explains. From the chunky wool rug to the bed’s sumptuous cashmere layers, “it feels like a super-luxe getaway,” says Clark. “It’s just zen.”