Koster Trench

The Koster Trench is the northern extension of the Norwegian Trench and the deepest point in Swedish waters at over 240 metres. Technical and advanced recreational divers descend the upper reaches of this submarine canyon to witness a deep-sea community rarely seen at accessible depths: stalked crinoids, large spider crabs, Norway lobster (langoustine) emerging from burrows, and at the shallower edges, dense horse mussel beds that host entire micro-ecosystems. The cold, oxygen-rich water produces exceptional clarity — a defining feature of Kosterhavet National Park.