I hope I'm not making any transgression by posting in this thread, but previous "Submarine" thread was "for everyone", so I hope same applies to this one.
Definitely not a nuclear boomer - in fact not a military submarine at all. In 1970s in Poland a demand has arisen for equipment capable of seabed research and drilling - reasons were twofold: prospecting for oil in Polish EEZ of southern Baltic, as well as geological support work during the construction of Gdańsk's Port Północny (Northern Port). Since conducting of such operations from the surface is very dependent on weather conditions, an idea was put forward to do it from below the surface, by means of drill installed on a bathyscaphe. First such vessel - Geonur - proved feasibility of the concept and was in fact very useful, but was eventually lost in 1980 off the shores of Senegal. As a replacement, Geonur II was built in 1981 - it's characteristic feature was a retractable tower that could house the drilling equipment (capable of reaching up to 30 meters inside the seabed). When used as a diver base it could dive to 150 meters, when used as drill it could dive to 80 meters, although from practical reasons it was usually limited to 100 meters, with operational depths of 60 meters being most common. Despite its usefulness, it was used operationally only until 1984 and in December 1997 was scrapped.
Poland, Geonur II