Research vessel that was converted into a fishing vessel in 1982.
When the ship was returning to port from fishing, the ship took on water in the strong wind and sank on 24 October 1985. Yvette, another fishing vessel nearby, was called for assistance and Thetis sank shortly afterwards. The crew escaped in the lifeboats and were later picked up by Yvette when she arrived at the site.

The wreck site is located at Tryggö, north of Smögen, which is a weather-sensitive area and strong surface currents often occur at the site.

There are many details to see and you can swim around the entire wreck in peace and quiet. Watch out for wires and cables aft. The trawl lies beyond the stern on the starboard side and continues down to the bottom. The wheelhouse is not intact because someone managed to get caught with the towline and tear off that section. It should be possible to penetrate the wreck. When the ship sank, the holds were filled with herring and reportedly there is still a lot of rotten fish in these spaces.