Kosterhavet National Park is one of Sweden’s most remarkable coastal destinations, combining clear saltwater, rocky islands, colourful marine life and quiet walking trails. Located in Bohuslän near the Norwegian border, this marine park protects a unique underwater landscape around the Koster Islands. Whether you want to kayak between skerries, watch seals, explore the seabed or simply enjoy a peaceful island day, Kosterhavet offers an unforgettable experience in Sweden’s great outdoors.
What is Kosterhavet National Park?
Kosterhavet National Park is Sweden’s first national park created specifically to protect a marine environment. It was established in 2009 and covers approximately 390 square kilometres, most of which is water. The park stretches along the northern Bohuslän coast, from the waters outside Strömstad towards the Norwegian border, and includes the sea around the Koster Islands.
The area is known for its exceptional marine biodiversity. Cold, deep water from the North Sea reaches the coast through the Koster Fjord, creating conditions that support species rarely found elsewhere in Sweden. Beneath the surface are rocky reefs, soft seabeds, eelgrass meadows and deep channels filled with fish, shellfish and other marine life.
Although the sea is the heart of the park, Kosterhavet is not only an underwater destination. Its islands and shoreline feature smooth granite rocks, salt meadows, small beaches, windswept vegetation and traditional coastal villages. Visitors can experience the landscape from a hiking trail, a kayak, a boat or a viewpoint above the water.
Where is Kosterhavet National Park?
Kosterhavet lies in northern Bohuslän, on Sweden’s west coast. The closest major town is Strömstad, a popular seaside destination with regular boat connections to the Koster Islands. The park is close to the Norwegian border, making it possible to combine a visit with a trip through the coastal regions of Sweden and Norway.
The Koster Islands form the best-known gateway to the park. The two main islands are North Koster and South Koster, known in Swedish as Nordkoster and Sydkoster. Smaller islands, skerries and exposed rocks surround them, creating a maze of waterways that is particularly beautiful when viewed from the sea.
Most visitors travel to the islands from Strömstad by passenger ferry. The journey takes you through the archipelago and provides an immediate introduction to the character of Kosterhavet. Boat schedules vary according to the season, so check current departure times before travelling, especially if you are visiting outside the summer months.
The Koster Islands
The Koster Islands are among Sweden’s most celebrated island destinations. South Koster is the larger and more populated island, with several small settlements, swimming areas, cafés, accommodation and marked walking routes. North Koster is smaller and generally quieter, with a more rugged character and several excellent viewpoints.
South Koster
South Koster is often the most convenient base for a first visit to Kosterhavet National Park. Ferries serve several landing points, including Ekenäs, where visitors can find the Naturum Kosterhavet visitor centre. The island has roads and paths suitable for cycling, and bicycles can usually be rented during the main visitor season.
From Ekenäs, you can walk towards beaches, rocky coves and viewpoints across the archipelago. The landscape changes quickly. One moment you may be walking through low woodland, and the next you may emerge onto an open granite shoreline with views across the Skagerrak.
North Koster
North Koster is a good choice for visitors who prefer a quieter island atmosphere. The island has fewer services than South Koster, but it rewards slow exploration. Walking trails pass through rocky terrain, coastal vegetation and small settlements before reaching open viewpoints over the sea.
The Koster Islands are largely free from ordinary car traffic, which helps preserve their peaceful character. Walking and cycling are the main ways to get around, although conditions vary by route. Some trails are uneven and rocky, so sturdy footwear is useful even on a short visit.
Why the marine environment is so special
Kosterhavet National Park has a richer marine environment than many other parts of Sweden. The Koster Fjord contains Sweden’s deepest marine waters, reaching more than 240 metres in places. Its depth allows water from the Atlantic and North Sea to reach the coast, bringing saltwater conditions that support unusual species.
More than 6,000 marine species have been recorded in the waters of Kosterhavet. Many are associated with deeper or more oceanic environments and are uncommon elsewhere along the Swedish coast. The park contains coral habitats, sea pens, sponges, anemones, starfish, crabs, sea urchins and a wide variety of fish.
The underwater landscape is especially important for scientific research and conservation. Some habitats are sensitive to disturbance, fishing pressure and changes in water quality. Protecting them helps maintain the ecological character of the west coast and supports the communities that depend on a healthy sea.
Marine animals to look for
Wildlife sightings are never guaranteed, but the waters and shores of the park provide opportunities to see a wide range of species. Harbour seals are among the most popular animals in the area. They can sometimes be seen resting on rocks or surfacing near boats and kayaks.
Porpoises also live in the surrounding waters, although they are more difficult to spot. Seabirds are common around the islands, including gulls, cormorants, eiders and oystercatchers. In shallow water, visitors may notice jellyfish, small fish, seaweed and crabs without needing specialist equipment.
Things to do in Kosterhavet National Park
Visit Naturum Kosterhavet
Naturum Kosterhavet at Ekenäs on South Koster is an excellent place to begin. The visitor centre explains the park’s marine habitats, wildlife and conservation work through exhibitions and educational displays. It is particularly useful for understanding what lies beneath the surface, since much of the park’s most important scenery cannot be seen from land.
Opening times and activities change throughout the year. During the busier season, Naturum may offer guided walks, talks, family activities and information about marine excursions. Check the official schedule before your visit.
Go kayaking
Kayaking is one of the best ways to experience Kosterhavet. A kayak allows you to move quietly through narrow channels, approach rocky islands and stop at small beaches that are difficult to reach by larger boats. The low position on the water also makes it easier to notice seabirds, seals and life in the shallows.
Conditions on the open coast can change quickly. Beginners should choose a sheltered route, check the weather forecast and consider joining a guided tour. Local operators may provide kayaks, safety equipment and instruction, as well as trips adapted to different experience levels.
Try snorkelling and diving
The clear saltwater around the Koster Islands can make snorkelling a rewarding activity, particularly in shallow bays and sheltered coves. Look for seaweed forests, small fish, crabs and starfish around rocky areas. The colours and variety become even more impressive below the surface.
Scuba diving offers access to deeper habitats and is usually arranged through specialist operators familiar with the local waters. Divers should follow all park regulations and avoid touching marine organisms or damaging fragile seabed habitats. Visibility depends on weather, currents and seasonal conditions.
Explore the islands on foot
Walking is a simple way to experience the land-based side of the marine park. Trails cross low hills, pine and deciduous woodland, open heath and exposed coastal rock. The islands are not large, but the terrain and frequent viewpoints make even a modest walk feel varied.
Popular walks connect ferry landing points with beaches, villages and coastal viewpoints. Allow extra time for pauses, photography and swimming. Some sections are rocky or uneven, and wet granite can be slippery after rain, so wear shoes with good grip.
Cycle on South Koster
Renting a bicycle can help you see more of South Koster in a single day. Quiet roads and island paths connect several parts of the island, although cycling is not suitable on every walking trail. Slow down near pedestrians and be prepared to leave your bicycle and continue on foot.
A bicycle is particularly useful if you arrive at one landing point and want to reach another part of the island before your return ferry. During the summer, rentals can be popular, so booking ahead may be sensible.
Swim from a rocky shore or beach
Swimming is a favourite summer activity on the Koster Islands. You can find sandy beaches, smooth rocks and sheltered coves, depending on which part of the islands you visit. The water is refreshing rather than tropical, even during warm weather, but a swim is a memorable way to experience the coast.
Take care around slippery rocks and changing weather. There may not be facilities at every swimming spot, so bring drinking water, a towel and sun protection. Leave the shoreline as you found it and take all rubbish with you.
Rules and responsible access
Kosterhavet National Park is protected for future generations, and visitors play an important role in keeping it healthy. Regulations can differ between land and sea areas, so follow signs and local guidance when exploring. The general principle is to enjoy the environment without disturbing wildlife or damaging habitats.
- Take all rubbish home and avoid leaving food waste on the islands.
- Keep a respectful distance from seals, birds and other wildlife.
- Stay on marked paths where requested, especially in sensitive vegetation.
- Do not collect shells, plants, animals or geological material.
- Use designated places for fires and check whether fires are permitted before lighting one.
- Keep dogs under control and follow local rules about leashes.
- Anchor carefully and avoid sensitive seabed habitats when boating.
- Follow fishing restrictions and all regulations applying to protected areas.
The national park is also a working coastal landscape. Local residents, commercial fishermen, researchers and visitors share the same waters. Showing consideration for boats, fishing equipment and island communities helps protect both the environment and the character of the area.
When to visit Kosterhavet National Park
Summer is the most popular time to visit, particularly from June to August. Ferries, cafés, bicycle rentals and guided activities are generally easier to access during this period. Long daylight hours make it possible to combine a ferry trip, a walk, a swim and a meal on the islands in one day.
Late spring and early autumn can be excellent for visitors who prefer fewer people and cooler temperatures. The islands may feel more peaceful, and the changing light can be beautiful along the coast. However, some services operate on reduced schedules, so planning becomes more important.
Winter visits offer a very different experience. Strong winds, short days and limited services make the islands less convenient, but the exposed coastline can be dramatic. Check transport information carefully and carry suitable clothing, food and navigation equipment if you travel outside the main season.
How to plan your visit
A day trip is enough to discover the main character of the Koster Islands, but staying overnight allows you to experience quieter mornings and evenings. Accommodation may include guesthouses, holiday cottages, campsites and other small-scale options. Availability can be limited in summer, so reserve early if you want to stay on the islands.
Bring practical supplies, especially if you plan to spend the entire day outdoors. Useful items include a refillable water bottle, packed food, a waterproof jacket, sun protection, insect repellent, comfortable walking shoes and a map. Mobile coverage and services may vary, and not every part of the islands has a shop or café nearby.
Before leaving, check ferry timetables, weather conditions and any temporary restrictions. If you are planning a kayak trip, dive or guided wildlife tour, book with an authorised local operator and ask what equipment is provided.
Getting to Kosterhavet National Park
Most visitors begin in Strömstad, which is connected by road and rail to other parts of western Sweden. From Strömstad, passenger boats travel to the Koster Islands. The route and stopping pattern depend on the service and season, so confirm the correct ferry for your destination.
It is possible to visit Kosterhavet by private boat, but navigation requires care. The archipelago contains shallow waters, rocks and narrow passages. Use accurate charts, respect marked channels and check local information before setting out. Kayakers should also understand tides, wind direction and the risks of exposed crossings.
Why Kosterhavet belongs on a Sweden itinerary
Kosterhavet National Park offers a rare combination of accessible island travel and genuinely wild marine scenery. You can arrive by public ferry, walk from a small harbour and soon find yourself beside an open horizon, far from traffic and city noise. At the same time, visitor centres, accommodation and local operators make the area approachable for first-time explorers.
The Koster Islands show how closely Swedish coastal life is connected to the sea. Their villages, boats, rocky shores and marine habitats form one living landscape rather than separate attractions. A visit is therefore more than a scenic day out. It is an opportunity to understand why Sweden protects this part of the coast and why careful travel matters.
Whether you come for a short walk, a day of kayaking or a deeper look at the underwater world, plan your visit with curiosity and respect. Kosterhavet rewards a slower pace, and its greatest experiences often come from simple moments: watching a seal surface beside a kayak, listening to seabirds above the rocks or seeing the evening light spread across the Koster Islands.