If you're in the been-there, done-that traveler club, here's something to add to your next itinerary: Kosterhavet, Sweden's first national marine park, has just opened. It's about 175 square miles, most of it open ocean, home to some 600 marine species. The park's northern water boundary is shared with Norway, and in fact Kosterhavet National Park runs right into Norway's new marine national park, Ytre Hvaler, which opened at the same time. Together, both parks encompass about 300 square miles.

Kosterhavet gets its name for the land that it surrounds, the Koster Islands, which are themselves a nature reserve. North Koster and South Koster are so close together that they really feel like one island, and together they're the westernmost settled area in Sweden. They're also ridiculously charming -- near the water, they're just what you'd picture a small Scandinavian fishing village to look like, and towards the center, it's all rolling countryside ripe for hiking and cycling, dotted with red-roofed houses.

But of course, the main event is what's below the surface. The water separating Koster Islands from Sweden's main land is actually a fjord, which achieves such a depth that it's home to deep sea species. Kosterhavet also includes Sweden's only cold-water coral reef, which makes for excellent cold-water scuba diving -- the rocky coast also means that there are also a number of shipwrecks to check out beneath the waves. Above the water, a sea kayak is the way to go --- take a look at Sweden's largest population of seals, and from a respectful distance, admire nesting areas for Arctic terns.