On the surface the water is fairly fresh, resulting in bathing areas that are free of jelly fish, while deeper the water has a higher salt concentration, with saltwater fish such as cod, pollock, flounder, and mackerel. The tide sets up one of Norway's strongest currents through the strait (outflow can reach speeds of 5 knots and the strait is known Selvikstrømmen (the Svelvik current) in Norwegian. Large ships can only sail in daylight and the largest only when assisted by tugboats.
On the surface, the water appears to be relatively fresh, leading to bathing areas devoid of jellyfish, whereas deeper in the water, it has a higher salt concentration, inhabited by saltwater fish such as cod, pollock, flounder, and mackerel. The tide generates one of Norway's most powerful currents through the strait (outflow speeds can reach up to 5 knots), known as Selvikstrømmen (the Svelvik current) in Norwegian. Large vessels can only navigate during daylight hours and are assisted by tugboats when sailing at their largest.