Skytteren

The ship Skytteren sank on April 1, 1942, about ten kilometres from the Swedish west coast near the city of Lysekil. The shipwreck is on the Swedish Maritime Administration’s list of environmentally hazardous wrecks in Swedish waters.

According to SwAM:s environmental risk assessment, Skytteren is ranked as number one on the list of the 30 most environmentally hazardous wrecks. An estimated maximum volume of 400 cubic meters of oil might remain in the wreck.

Investigations of the shipwreck

In 2005, the Swedish Coast Guard performed an investigation of the wreck using a remotely operated underwater vehicle (ROV). Results showed that joints in the hull were corroded and that oil was leaking from a fracture in the hull.

In the autumn of 2018, SwAM and the Swedish Navy carried out a joint investigation of Skytteren for eight days (14-21 November). Since the shipwreck is located at a depth of approximately 74 meters, in an area with strong sea-floor currents, SwAM considered that the Navy’s divers where most suited for the task. The investigation was carried out from the Submarine Rescue Vessel HMS Belos. Deep divers participated from The Swedish Armed Forces Diving and Naval Medicine Centre, the 1st Submarine Flotilla and the 4th Naval Warfare Flotilla, as well as doctors and nurses for medical preparedness.

During June-August 2020, further work was carried out on the wreck. With a high-quality camera mounted on an underwater robot, all parts of the 172 meter large wreck were digitally documented with almost 27,000 overlapping images. With a computer technology called photogrammetry, the digital photographs were assembled into a high-resolution image, which makes it possible to both get an overview of the entire wreck and to study specific areas at a detailed level. This data was initially used to study the extent of degradation of the wreck, and during the inspection for presence of oil in, as well as in the salvage operation of the oil.

A third survey was conducted during February-March 2021 with the aim of discerning if, and where, the oil in the wreck is located. Divers performed about 60 penetrations of the hull at three different depths horizontally along the hull side. Where oil was found, a probe was inserted to enable a calculation of the lowest volume of oil in the tank in question. The penetration holes were re-sealed immediately after the examination of the tanks. However, it was not possible to examine the fuel tanks on the port side of the ship, since these tanks are located at the bottom towards the seabed. The data from this operation will be essential in the future salvage operation of the oil from the wreck.

A salvage operation of oil and ghost nets will be carried out on the wreck starting in mid-September 2021.

What did the investigation show?

The purpose of the investigation in 2018 was to obtain more information for the risk assessment tool VRAKA for the assessment of environmentally hazardous wrecks. Hull thickness measurements were carried out where the fuel tanks are located. The divers searched for distinct changes or damages to the hull. The wreck was video- and photo documented to obtain data for a future oil recovery operation.

Skytteren seemed to be in a relatively good condition at a first glance. However, measurements on the hull plates showed that they are heavily affected by corrosion and that they in specific areas only are 5 - 6 millimetres thick, which is less than one third of the original thickness. On the sea surface, a small but continuous oil spill was also detected during the investigations. It was not possible to backtrack where on the wreck the oil leaked from or to draw any certain conclusions on the amount of oil left in the wreck during this investigation.

The investigation in 2020, and the analysis of the material (orthoimage and Digital Elevation Model, DEM), showed that the wreck's hull is still relatively complete but with signs of severe corrosion in some places. The stern is in worse condition than the rest of the wreck. There are several holes due to corrosion but also a 4.2 meter long crack in the hull. In this area, the hull has a depression with a difference of 90 centimetres compared to the rest of the hull. This indicates a weakening that could lead to an impending collapse. The bilge keel has also been carefully examined, as this area is particularly interesting. Since the wreck is on the side, the bilge keel is the highest point of the wreck, and therefore where the oil may have accumulated if leaked from the bunker tanks. No holes or damage to the hull was discovered in this area.

Cost of measures taken

The cost of the investigation of Skytteren in 2018 amounted to SEK 1 799 609, in 2020 to SEK 1 548 000 and in 2021 to SEK 7 000 000. The funds come from the Swedish Government's budget 1:4 for the Remediation and restoration of contaminated areas.

Here is a map of the most environmentally hazardous shipwrecks in Swedish waters.

Videos from Skytteren

See SwAM's youtube channel for videos from the diving investigation.

Photos from the investigation

Slideshow from the investigations of Skytteren. Photogrammetry images rendered in 2020 and photos from the press event on November 21, 2018, which attracted some 20 journalists.