The park contains the only known living coral reefs in Sweden, located in the deep waters of the Koster Fjord.
The water salinity in Kosterhavet is significantly higher than in the rest of the Baltic Sea, allowing Atlantic species to thrive here.
The Koster Fjord acts as a natural trap for organic material, providing a nutrient-rich environment for deep-sea fauna.
Kosterhavet is part of a larger cross-border marine protected area that connects with Norway’s Ytre Hvaler National Park.
Over 200 species found in the park are not found in any other Swedish marine environment.
The area features a rare 'threshold fjord' structure that restricts the exchange of bottom water, creating a unique deep-sea habitat.
Kosterhavets Nationalpark is Sweden's first marine national park, covering 38,878 hectares of sea and land along the coast of Strömstad and Tanum. The park protects a unique marine environment characterized by the deep Koster Fjord, which reaches depths of 247 meters and features a direct threshold to the Atlantic. It hosts approximately 12,000 species, including rare deep-sea corals and cold-water coral reefs found nowhere else in Swedish territorial waters. The landscape includes the Koster Islands, featuring granite skerries, coastal heaths, and a distinct lack of road traffic. The area is influenced by the Jutland Current, bringing high-salinity water and rich biodiversity into the archipelago. It is managed by both the Swedish Environmental Protection Agency and the County Administrative Board of Västra Götaland. Visitors access the park primarily via water-bound transport through the Koster Islands. The ecosystem supports a vast array of marine life, from microscopic plankton to large marine mammals.
The viewpoint at Valfjäll on South Koster for panoramic views over the archipelago.
Bring polarized sunglasses to better observe marine life through the clear water surface.
Carry sturdy footwear for navigating the uneven, moss-covered granite rocks of the archipelago.
Bring a waterproof bag for your gear, as island hopping often requires boat travel.
Attempting to reach the outer islands without checking local marine weather forecasts for swell and wind conditions.
The park is open year-round, but visitor facilities and ferry services significantly scale back during the winter months.
Strict 'leave no trace' policy applies; do not remove stones, shells, or plants. Protect nesting birds during the spring.
