It turns out there is another tank in Czarna Nida River in Poland. The Bergepanther was dragging an evacuated tank Panzer IV behind it, and a another suprise elements of Sdkfz 251D
R-1 tank - Wikipedia
R-Tanks | Midwest | ASP Enterprises
Underground Detention & Retention Systems | R-Tank & StormChamber | Houston, Austin, San Antonio, Dallas, New Orleans | Construction EcoServices
R-Tank Teaser | Can anyone guess what type of R-Tank modules these are? We're excited to be on site and filming this install - so stay tuned for a full install video...