Havets Hus ("House of the Sea") is a compact aquarium on Lysekil's waterfront dedicated entirely to local cold-water marine life. The centrepiece is a 140,000-litre tunnel tank where small-spotted catshark, cod, and goldsinny wrasse swim around you, and there are smaller tanks of touch-friendly starfish, jellyfish, and the sometimes-camera-shy lumpsuckers that are the unofficial mascot of the place.
It is small enough to see in about an hour and well done for what it is — heavily oriented toward children but also useful for adults wanting to understand the Skagerrak ecosystem before a boat trip. Open daily in summer; reduced hours October to March. Admission around SEK 175.