The Mast Wreck

– abstract of the field report

by Torleif Nilsson

Five kilometres east of Gamla Oxelöund at the Bråviken Bay, Swedish East Coast, there is a remarkable wreck on ca 30 m depth. The wreck site is in a military area where no anchoring or diving is permitted to the public. The wreck was discovered by the author during a 1992-94 wreck survey project.

mast top

Diver at the top of the standing mast. Note the pulley block still in position. Photo: Torleif Nilsson.

Unique wreck in the Oxelö archipelago

Even by the high standards of preservation in the Baltic Sea, this wreck is unique in several aspects. This 17 m long and 5 m wide carvel-built ship stands deeply embedded in the bottom sediment with no apparent list and seems to be totally untouched since its sinking about 250 years ago. The ship was two-masted and the main mast is still standing in its full length. On the badly worn deck, there are several fallen-down rig details, near their original locations. Most of the ship’ interior is covered by mud, but in the stern section, clay pipes, wine bottles and other domestic items have been observed.

    The 17 m high main mast is intact after 250 years on the bottom. Illustration: Göran Ullrich.

site drawing

The Mast wreck offers unique opportunities to provide detailed knowledge about shipbuilding and life onboard an 18th century merchant ship. After the sinking, the ship seems to have landed almost undamaged on the sea bottom. It is not unlikely that the complete rigging remained more or less intact for some time, before it rotted away, and the rigging fell straight down on the deck.

The typical Baltic wreckfind has either been smashed at the sinking or damaged later by the forces of nature or human activity. Many wooden wrecks in the Baltic Sea look more like piles of planks, where the parts often have been stirred around.

In this case we have instead a wreck that seems to be more or less untouched and where most of its information is preserved. This is manifested by the standing main mast. Indeed it is worn by time and several parts have fallen off, but this process has been very gentle. All loose parts remain close to their original locations.

Already at the first dive in 1994, it was obvious that this wreck needed an immediate investigation. It was well preserved but at the same time looked very fragile. It seemed to approach a stage of accelerating collapse.


At the stern we located several 18th century wine bottles. Photo: Torleif Nilsson.

Computer generated models

During 1994-96 extensive video and photo documentation was made as well as measuring of the wreck. From this data a three-dimensional model was created using the CAD programs Pro/Engineer and Pro/Mechanica. Based on the CAD model and the video footage, the skilled artist Göran Ullrich made several accurate images. These images have been a great aid, considering the limited visibility at the actual site. The drawings are quite detailed, but still preliminary. Several measurements may change during the course of investigation.

CAD drawing

A simplified 3D CAD model, made from measurements as well as video and photos. By Torleif Nilsson.

1997 fieldwork

During 1997 a permit was given to take samples, for dating the ship. Several wood samples, pine and oak, were taken for dendrochronology analysis. One glass bottle was brought up from the group of 13 bottles that lay openly in the stern section. The initially planned probing of the hold was cancelled following soundings with a thin rod. This indicated that the content of the hold was too compact to penetrate.

clay pipe

Clay pipe salvaged in 1997 for dating analysis. Photo: SSHM.


The dendro analysis has been made by Alf Bråthen, bottle treatment and conservation by Ingrid Hall Roth (Vasa Museum), bottle analysis by Lars Westergren, and clay pipe analysis by Arne Åkerhagen. They have all helped the project by doing this free of charge. The analyses suggest that the ship was built and sank during the first half of the 18th century.


Just aft of the hold two pumps are sticking up. Photo: Torleif Nilsson.

1998 fieldwork

During the summer of 1998 the documentation continued. Also, the main mast was braced and stabilised with new rope. This was important not only for the wreck but also for the divers’ safety. A permit was also given to salvage the remaining visible bottles, since they are fragile and at risk of being crushed by future collapsing parts of the ship.

Future work

There is no lack of things to do. But presently, the main task is trying to finance future investigations, as well as the cleaning, conservation and analysis of the items already salvaged. One of the remaining questions is the cargo. Is it possible to tell without excavating the entire hold? Is there a way to measure the shape of the lower hull which is embedded in the seabottom?


In the stern, where the living quarters were, remains of the galley can be seen. Photo: Torleif Nilsson.

The Mast Wreck Association

This association was founded in 1997 as a means to find sponsors for the further work. So far, support has been given by the cities of Nyköping, Trosa and Oxelösund, as well as the county of Södermanland. We have also been given generous help by Crimson AB, Södermanlands Nyheter, Södermanland County Museum, SSAB, Fastighetsbolaget Nötknäpparen i Nyköping, Sandvik Handtools AB, Sjöfartsverket, and Oxelösunds hamn AB.

Torleif Nilsson

abstract of the original report in Swedish,
translated by Per Åkesson, Feb '99


Sonogram 1 (bow upwards) and sonogram 2 (stern upwards) by Sture Hultquist.

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