fun on the Biggesee, Germany, 1980s

Or in English, Lake Bigge, in Westfalen, an artifical lake created for a hydroelectric power station in the 1950s and it provides resevoir water for the Ruhr district.  The Salonschiff or saloon ship Bigge in the pic was built in 1982 and substantially added to in 1993.  Pics and plans of its present appearance here.