Kosterhavet National Park, Bohuslan Travel Guide

The sea that made the park

Kosterhavet is defined by water: a deep, salt‑rich trench where Atlantic currents meet the Scandinavian coast to create unusually clear, cold waters and a marine landscape more commonly associated with temperate reefs. The underwater topography includes the Kosterfjord — a channel reaching depths well over a hundred metres — and ledges, walls and boulder fields that host cold‑water corals, sponges and dense kelp forests that sway in the currents.

Date of origin and conservation role

Established in 2009 as Sweden’s first marine national park, Kosterhavet was created to protect a unique biodiversity hotspot on the Skagerrak seaway. The park’s protected waters and adjacent islets conserve habitat for species that are rare or absent elsewhere in Swedish waters, and they form an ecological bridge to neighbouring protected seas across the Norwegian border.

Life above and below the surface

Above the waves the Koster Islands provide a patchwork of rocky shorelines, sheltered bays, meadows and small woodlands; beneath, forests of brown algae and eelgrass meadows shelter juvenile fish and invertebrates. Researchers and naturalists have recorded thousands of marine species here, from sea anemones and starfish to commercially and ecologically important shellfish, and even reefs of Lophelia-like cold‑water coral that create three‑dimensional habitats for other organisms.

Human footprint and island character

Nordkoster and Sydkoster — the two main inhabited islands close to the park centre — are low‑lying, wind‑scoured and largely car‑free, with narrow tracks, farmed meadows and small harbours. Small red and white wooden houses cluster near the piers and a handful of local cafés, guesthouses and outfitter services cater to visitors who come to hike, cycle, kayak and dive. The islands’ human presence is small in scale and oriented toward outdoor life and marine tradition.

Visitor centre and interpretive resources

Naturum Kosterhavet, located near the Ekenäs jetty on South Koster, acts as the park’s main entrance. The centre combines exhibitions, short films, microscope stations and an aquarium with a touch tank that brings the marine world within reach. Staffed year‑round, the naturum offers seasonal guided activities, family programmes, and interpretive materials that explain geology, currents, and the special species that define the area.

What to expect on the water and shore

Approaches from Strömstad and mainland piers reveal an archipelago of rocky islets and wide sea lanes. On shore you’ll find rocky bathing ledges, sandy coves and paths that thread between meadows and rocky outcrops; on the water divers and snorkellers encounter exceptional visibility, kelp canopies and dense animal life. Conditions change with tides and wind, so the park’s regulated zones, snorkel trails and seasonal rules are designed to balance recreation with fragile habitat protection.