Mysterious underwater barriers in Blekinge

The underwater image shows the remains of an underwater barrier outside Karlskrona. The photo was taken by Jim Hansson, SMTM.
Key learning

In the water outside of Blekinge, you can find upright standing wooden poles fixed on the bottom of the sea. With tops ending just below the water surface, they form some sort of underwater barriers.

So what are they, and why are they put there?

The short answer…

Today we know that those mysterious wooden structures prevented ships from entering a port or passing strategically vital waterways, says marine archaeologist Mikael Björk.

Strategic line of defence at risk

However, the once so important barriers risk disappearing due to natural and human factors.

Furthermore, potentially rising water temperatures in the Baltic Sea pose another challenge. In that case, the shipworm (teredo navalis) can gain a foothold and destroy wooden wrecks, submarine forests – and the submarine fences.

A knowledge gap

So, the time when the barriers physically remain in the Blekinge archipelago may be limited. Also, in general, the knowledge of the underwater barriers is low and based solely on smaller surveys carried out during the 1960s and 1990s.

Therefore, in 2022 and 2023, Blekinge Museum will carry out a project depicting why the barriers were constructed at certain places and investigate other probable premises.

Mikael Björk leads the project, and the work will also include describing the religious, economic, and physical landscape at the time.

We support the archaeological project that maps the marine cultural landscape in Blekinge to help fill the knowledge gap.

MArtin Widman – Voice of the Ocean
Martin Widman at Voice of the Ocean

We support the archaeological project that maps the marine cultural landscape in Blekinge to help fill the knowledge gap.

MArtin Widman – Voice of the Ocean
Martin Widman at Voice of the Ocean

Hands-on inspections

The submarine wooden structures must be physically examined by divers to determine the extent of the barrier, date it, and determine which tree species are included.

Each barrier is placed in a larger context where marine and land archaeology are integrated. This is to conceive an idea of ​​the reasons for the constructions and how it was used.

It is simply about man’s relationship to the sea and the cultural landscape, says marine archaeologist Mikael Björk.

The map shows the area to be investigated in 2022 – an underwater barrier complex called Trekant located east of Torkö in Ronneby municipality. The map comes from the Swedish National Heritage Board.
The map shows the area to be investigated in 2022 – an underwater barrier complex called Trekant located east of Torkö in Ronneby municipality. The map comes from the Swedish National Heritage Board.

The project is linked to Blekinge Museum’s long-term strategy to build and disseminate knowledge. With the new knowledge, says Mikael, we will better understand how Blekinge and Southern Sweden have developed from the late Iron Age. And how trade routes and power centres have evolved over the centuries.

After the project is completed, it will be presented to the general public and shared with researchers through several initiatives – such as reports, lectures and an exhibition.

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*The underwater image shows the remains of an underwater barrier outside Karlskrona. The photo was taken by Jim Hansson, SMTM.