Bornholm · Denmark · Wall
Ertholmene
Baltic wall diving to 30 m, with a seal colony on the skerries
Photo: Arne Møller Jensen · CC BY-SA 2.0
Ertholmene is a small archipelago about 20 km north-east of Bornholm, and what VisitBornholm lists there is wall diving to a maximum of 30 m, one of the two deepest dives on its Bornholm list. The islets are Natura 2000 site no. 189, and the skerry Tat carries a grey seal colony that has grown quickly since the late 2000s. Every dive here starts with a boat crossing.
Where it is and how deep
55.3200° N, 15.1878° EApproximate position — the dashed circle shows where the site lies; your operator's briefing has the mooring.
The dive
The islands sit about 20 km north-east of Bornholm, so the dive begins with a crossing, and what VisitBornholm lists here is the wall — rock going down rather than sloping away — to a maximum of 30 m. That is deep for the Baltic, and deep enough that the profile rather than the conditions sets the length of the dive. No published source describes an entry point or a route along the wall, so the detail comes from whoever runs the boat.
Grey seals are the animal to look for. The colony on the skerry Tat was put at around 40 animals in 2009, at least 80 in 2010 and at least 180 in 2011, enough that it is counted as a drag on local fishing, so an encounter is a real possibility rather than a story — on the seals' terms, and not something a dive plan can promise. Tat and Græsholm are closed bird sanctuaries with no public landing, and the whole archipelago is Natura 2000 site no. 189.
Marine life and season
- Seals & sea lions
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Fair | Fair | Fair | Good | Good | Prime | Prime | Prime | Prime | Good | Fair | Fair |
Season follows Bornholm: Jun–Sep is warmest and calmest; late winter gives the clearest water, and the Baltic can ice over in hard years.
Know before you go
- The wall runs to 30 m in cold water, which puts a hard limit on bottom time: plan gas and ascent for the depth rather than for the profile you would dive in the shallows.
Photos from Ertholmene
Wbartoszy · Public domain
Arnoldius · CC BY-SA 4.0
7alaskan · CC BY-SA 3.0
Questions divers ask
How deep is the wall at Ertholmene?+
VisitBornholm gives 30 m as the maximum on the wall dive at Ertholmene. That makes it one of the deepest dives on its Bornholm list and an advanced-level profile in cold water.
Are there seals at Ertholmene?+
Grey seals use the skerry Tat. The population there was estimated at about 40 animals in 2009, at least 80 in 2010 and at least 180 in 2011, and it has grown enough to affect local fishing. Tat itself is a closed bird sanctuary, so there is no landing on it.
Sources
- Ertholmene — Wikipedia (da)
- Diving on Bornholm: discover Denmark's underwater wonders — VisitBornholm
Photo credits
- Aerial view of Christiansø's stone harbour with sailboats moored between red-roofed houses. by Arne Møller Jensen, CC BY-SA 2.0, via Wikimedia Commons
- Bladderwrack fronds swaying underwater in the shallows off Frederiksø. by Wbartoszy, Public domain, via Wikimedia Commons
- The Store Tårn lighthouse on Christiansø, seen from the coastal footpath. by Arnoldius, CC BY-SA 4.0, via Wikimedia Commons
- Weathered granite skerries breaking the surface east of Christiansø. by 7alaskan, CC BY-SA 3.0, via Wikimedia Commons
In The Logbook
- Where to dive with seals and sea lionsBig animals · 17 min read
- Cold-water diving: is it worth the drysuit?Cold water · 8 min read
More dive sites in Bornholm
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