In the 1930s, the Soviet Union built a series of submarines called the S class, based on German designs.
In the summer of 1942, the S7 sank the Swedish cargo ships Margareta and Luleå, delivering iron to Germany. Shortly after, the sub was cruising on the surface at night, off the Swedish coast not far from Norrtälje, when she was spotted by the Finnish sub Vesihiisi. The Vesihiisi fired one torpedo and the S7 sank quickly.
Four survivors who were standing in the conning tower were rescued by the Finnish sub. They were taken prisoners. Among them was the commander Sergey Lisin.
In July 1998, the S7 was located with side scan sonar on 40-45 m depth off Söderarm in the Stockholm archipelago.
The 78 m long sub is intact except for the stern, where the torpedo hit. The conning tower and the stern hatches are closed, so nobody knows what it looks like inside. Before she was hit, the S7 had closed all hatches and was preparing to dive. So the inside, a grim grave, may still be dry.
The research team consisted of : Anders Jallai (research and photo), Johan Candert (film), Ingvald Eckerman (research), Sture Hultquist and Per Hedlund (sidescan), Björn Rosenlöf (diver), Thomas Fagerholm (diver), Micke Sundin (skipper), and Leif Skals (mate).
Sonograms by Sture Hultquist
The upper part of this image shows a direct reflection (difficult against a round hull) and the lower part the sonar shadow.
The image is a combination of a view of the wreck from the surface and a view from the side, at the seafloor level. It is a geometrical effect of the way the sidescan sonar works.
The stern is destroyed and there is also great damage just forward of the tower.
The direct sound reflection is bad since the hull is covered by a 2 cm layer of rust. However, the shadow of the submarine is clearly visible against the seafloor. The shadow shows:
Fish similar to the one Sture Hultquist used for side scan sonar.
The Swedish daily paper Aftonbladet has an excellent web publication. Here are some archive articles in Swedish. Among other, there has been an interview with Vasily Subbotin, the only surviving Russian crew member.
Mr Subbotin toasts in vodka to his dead comrades.
Per-Olof Ekman: Havsvargar (Schildts, 1983)
Alexej Smirnov: Svensk historia under vatten (W&W, 2002).
Article in Pravda, Moscow, 8 August 1998
Dagens Nyheter, 30 October 1942
Dagens Nyheter, 1 August 1998
by Per Åkesson, Aug 1998
sonograms published by kind permission from Sture Hultquist, page rev apr '10
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