The rugged coast of Georgian Bay isn’t an easy place for a building to make a mark. Here on the northeastern side of Lake Huron, clear water laps up on solid shores of pink granite studded with wind-bent pine trees. It seems that architecture can’t add much to this rough, gorgeous landscape.

That was the dilemma for Becca and Doug Worple, a Cincinnati couple who spend summer vacations in this region of Ontario. “This place is my heaven,” says Becca, who has made the trip every year of her life. “Every day is unpredictable and magical.” Summers are warm and clear, but the winds, she points out, can change at any time.

Change came for the couple several years ago, when they decided to strike out from the island that Becca’s family owns and find a getaway for themselves and their children, Owen and Emma. They grabbed onto a rare opportunity to acquire a U-shaped, three-acre chunk of rock in Pointe au Baril, with two aging cottages and a two-story boathouse. The island, Becca says, “was a bit scary. It looked like a lot of work. But you could tell that somebody had loved it once.”

The Worples were planning to rebuild in the typical style of the area, where some families have been spending extended summers for many generations. But they soon realized that they had a major project on their hands, and they’d have to get creative. “Generally, you give the contractor your paper illustration of what you want and he makes it happen,” Becca says. “But this boathouse wasn’t even safe to walk through. I knew I couldn’t do a little paper drawing of that.”

Good fortune connected Becca with the architects who would provide the answers. Trying to search online for an architect recommended by a friend, she found Michael Meredith of MOS, a young interdisciplinary practice then based in Toronto. “It was a sort of wrong number,” Meredith recalls with a laugh. “She was calling for a Martin Miller or something, with a name similar to mine.” But Meredith and his partner Hilary Sample were intrigued by the project. “So I said, ‘Come up!’” Becca recalls. “I showed him what island living is like.” Living in this area is about low-key enjoyment of the landscape and deep social ties—the Worple kids are friends with the children of Becca’s childhood pals.

Meredith and Sample, both young teacher-architects, quickly accepted the challenges of the job: a rocky island that’s a 20-minute boat ride from the mainland, a climate where temperatures range from below zero to 100 degrees Fahrenheit, and a site that endures powerful westerly winds in the wintertime. “It’s amazing how extreme nature is up there,” Meredith says.

They proposed a series of buildings that would form a “necklace” around the island–a main cottage and a series of outbuildings that could accommodate the many overnight guests that go with summers in the area. For the first building, a two-bedroom sleeping cottage completed in 2005, they chose materials and shapes that wouldn’t stand out. “They’re really simple, almost Platonic forms,” Meredith says. The modest cabin has boat,a gabled roof and a cladding of untreated cedar, a material that shows up on docks and homes along Georgian Bay. “Allowing the buildings to weather seems the right thing to do,” Sample says. And it’s ready for winter: Sliding barn doors seal the place up as an impenetrable box.

Inside, the walls, floor, and ceilings are wrapped with warm-hued Douglas fir, and a fireplace is made out of local stone. The architects and some of their students from the University of Toronto handmade the bathroom fixtures: a massive bathtub and a broad, shallow sink, both sculpted beautifully from iroko wood. The relatively simple construction incorporates clever sustainable design: A two-level wood roof structure keeps the sun’s heat away from the interior, and small windows at either end facilitate powerful cross-ventilation. It’s natural air-conditioning, and it works beautifully.

Meredith and Sample—who now teach at Harvard and Yale, respectively—clearly poured themselves into the project. Along the way they provided an education for Doug, founder and creative director of an ad agency, and Becca, a photographer. Meredith “totally changed our way of thinking,” says Becca. “I started learning more about architecture and why it is what it is today. I wanted something traditional, but with building materials what they are, you can approach it in a totally different way. If you have that opportunity, why not go for it?”

Their next step was to do something wilder: to build a house not just on the water but actually in the water. Thanks to the old boathouse’s footprint, the Worples had the right to build a decent-size structure within the island’s cove. Meredith and Sample designed a waterborne two-story building supported by massive pontoons. That solved some of the problems of building in such a remote location: The pontoons and a skeletal frame were floated to the contractor’s workshop a few miles away for further framing while the lake was frozen and then tugged back to the site for the remainder of construction. “It was almost prefabrication, but not quite,” Meredith says.

The finished building is the family’s summer headquarters, despite its modest 1,250 square feet of indoor space. Downstairs are a boat slip, storage, and sauna; upstairs there are two bedrooms (the kids have bunkbeds), an office, and a galley area, with dramatic views from parallel windows. As Sample explains, the boathouse is the nucleus of the whole island. It’s connected to the island from the second floor by a bridge that reaches toward the nearby sleeping cabin and at water level by a dock that connects to the other side of the cove. An outdoor stair is open to the sky above and the water below.

“The ability for the boathouse to float,” Sample says, “is also a response to the climatic reality that the water is always fluctuating and changing.” Indeed, the levels of the Great Lakes rise and fall rapidly, more dramatically in recent years thanks to climate change and other human interference. Though such changes can be harsh on waterfront buildings, the Worples’ place is secure. And, Becca says, fantastic: “I like the gentle rocking of it, and I love being right on the water,” she says. “I woke up one morning and there were a bunch of kayakers right out the window. It’s like you’re on a boat.”

The whole building is clad in the same raw cedar as the cabin, and a network of slats wraps some of the windows and the outdoor staircase. “At first I thought it was a terrible idea,” Becca admits. “Why would you block an amazing view? But there are reasons—to force a view or to create an illusion.” In fact, Sample says the designers made a conscious effort to provide a variety of visual experiences. “You don’t want to see it the same way all the time,” she says. “From the sleeping cottage, we framed a tree so you didn’t have the same panorama you saw elsewhere.” In that respect they took some cues from Becca’s many photographs of her family at play and the landscape. “It gave us an idea of what they see,” Sample says, “and we tried to incorporate that into the design.”

It clearly worked. While the Worples’ cottage is unusual in the area, nowadays Becca doesn’t see it as radical at all. “In the end I like how understated it is,” she says. “Everything up here is about blending in with the environment, and that’s exactly what this place does.”