Six years ago, the shoreline in Kastrup, Denmark was practically inaccessible, not that anyone wanted to go there: It was nothing but industrial buildings and rocky beaches. The parklike Copenhagen waterfront to the north was the envy of Kastrup residents, so in 2003, the city hired Swedish design firm White Arkitekter to clean up its coast. The result: the Kastrup Sea Bath.

What was once considered the wrong side of the harbor is now a bustling hub of activity, a result of the recent extension of the Copenhagen Metro through Kastrup, the replacement of the beach’s rocks and stones with white sand, and the completion of the sea bath in 2005. Teenagers swarm the structure in the summer, jumping off the diving platforms. Even in the winter, when temperatures dip down to the 30s (Fahrenheit), hardy bathers still stop by for a quick dip or, more frequently, to soak up the sun on the built-in benches.

From the beach, the bath’s 328-foot pier extends into the Øresund Strait toward Sweden and culminates in the 9,365-square-foot swimming, bathing, and diving structure. The spiral plan, which was inspired by the shape of a conch but also meant to mimic the motion of ocean swells, offers a range of in-and-out options: ladders, stairs, and ramps in various widths that disappear into the lightly lapping waves and jumping platforms at all heights. The sandy bottom is six to ten feet below the surface in most areas, 15 feet under the highest diving platform. Swimmers who come for an aquatic workout do 245-foot laps around the structure’s inner circumference.

Along the first level, past the benches and stadiumlike seating, are gender-specific changing rooms—–but they’re rarely used, says Fredrik Pettersson, the lead architect of the Kastrup Sea Bath project. Instead, bathers strip down to their skivvies on the beach or on the deck. “The Danish have a tradition of public bathing. Being naked is not a problem,” Pettersson says, though he admits a preference for swim trunks.

The slatted outer wall wraps around the structure and provides protection from the wind while still allowing a view across the strait to Malmö, Sweden. “The spaces between the slatting are small enough that kids can’t get their heads stuck in them but large enough to enjoy the lively urban place, with the traffic through the Baltic Sea, the planes above, and the kayaks below,” Pettersson says.

Building in open water presented a unique set of challenges. During construction, workers often dropped their tools into the water, therefore Pettersson devised a system of strings and magnets to fetch those that didn’t float. Shipworms, just like terrestrial termites, can quickly destroy soft woods, so the architects carefully researched the materials, choosing azobe for its durability and strength against saltwater and the pests. The wood is also resistant to human wear and tear—–both natural and criminal. Because there’s no finish on it, graffiti can easily be sanded off, and the azobe quickly returns to its brown-gray color. The stairs and ramps that dip into the water require regular scrubbing to minimize the buildup of moss, a slippery hazard to swimmers, but otherwise the structure requires little upkeep.

Kastrup is not alone in its quest for urban renewal and waterfront rejuvenation: Stockholm’s updated waterway is slated for completion in 2010, and both Philadelphia and New York City have recently pushed forward efforts to redevelop theirs. Though in the United States, we might not share the Danes’ time-honored tradition of public bathing, the Kastrup Sea Bath presents a strong case for dipping our toes in the water.