Mystery Underwater Device Lost By U.S. Navy in Adriatic Sea.

[Haenk]

Replying to myself, there is an update to the story (in German):

https://weather.com/de-DE/wissen/umwelt/news/2020-02-18-teil-von-geomar-unterwasserobservatorium-geborgen/?par=focus_web_main

In short: They found one of the two parts only 180m away - however in 20m depth, with very little sight. They used a special purpose ship for detecting shipwrecks and ocean mapping. Assuming an illegal fishing trawler picked them up by accident...