Kostersten is a cluster of small skerries just north of Nord Koster, dived from a boat for the rock around them. The north and east sides are clean rock walls sloping down toward the Koster fjord, while the south and south-west side is a boulder rockfall running out into sloping sand. The listing gives a maximum of 50 m and more.
Where it is and how deep
58.9477° N, 11.0192° EApproximate position — the dashed circle shows where the site lies; your operator's briefing has the mooring.
The dive
Kostersten is a few small skerries north of Nord Koster, and which side you dive gets decided on the day by wind and current. On the north and east sides the rock stands as clean walls that slope down toward the Koster fjord, so you can pick a depth, run the wall along it and let the rock handle the navigation for you.
The south and south-west side is a different dive: a rockfall of boulders that runs out into a sloping sand bottom with stone and rock sections scattered through it, which is the side to take when you would rather work slowly and look into gaps than cover distance. The listed maximum here is 50 m and more, so the depth you dive is one you set yourself.
Marine life and season
The sources we used don't single out particular species here.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Good | Prime | Prime | Good | Good | Good | Prime | Prime | Prime | Good | Fair | Fair |
Season follows Bohuslän & Gullmarsfjord: Late winter gives the clearest water once the plankton dies back; Jul–Sep is warmest and easiest for shore entries.
Know before you go
- The surface current can run very strong here, so plan the entry and the pick-up around it and get down rather than waiting on the surface.
- The site is very weather-sensitive and is one of the first to come off a schedule; check the forecast before committing the boat to it.
Questions divers ask
How deep is Kostersten?+
The listing gives a maximum of 50 m and more. The walls on the north and east sides keep dropping toward the Koster fjord, so the depth you dive is the one you choose rather than one the site sets for you.
Sources
- Kostersten dykplats — dykarna.nu
- dykarna.nu dive-site KML export — dykarna.nu
In The Logbook
- Cold-water diving: is it worth the drysuit?Cold water · 8 min read
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