Rhein-Neckar Rowing
There are a large number of rowing clubs in the Mannheim area. If you click on the albums you'll see GPS coordinates in the captions. The names resemble those in the US:
Ruder-Club & Ruderklub = rowing club
Rudergesellschaft = rowing company
Ruderverein = rowing association
Regattaverein = regatta association (organize regattas)

The Mannheimer Regattaverein includes the 5 Mannheim clubs, plus Ludwigshafen and Frankenthal.
Doug joined the Mannheimer Ruder-Club, which is the oldest. Not necessarily because it is the oldest, but because a friend introduced him to a member. Also, their club house is the closest to the John Deere factory where Doug works. Though Amicitia and MaRuBa are also very conveniently located near the city center.
A few of the clubs (MRC, LRV, RG Speyer, Worms) have main club house buildings on the Rhein River, but since the water gets rough they only serice Gig boats. The clubs then maintain other boat sheds on protected parts of water - typicallz Altrhien or older parts of the Rhein channel that don't have any current anymore.