If that ain't Lake Minnetonka in "Purple Rain," which lake is it?

In 1984's "Purple Rain," Prince famously tells Apollonia to purify herself in the waters of Lake Minnetonka. They're standing by a lake, so she jumps in, and only then does he tell her "That ain't Lake Minnetonka." I believe it's not--I'm a native Twin Citian and Lake Minnetonka is huge and ritzy. But my question is: What lake IS it? Another Twin Cities lake? Something in L.A.? A soundstage pool? (Unlikely!) Does anyone have the definitive answer. You can watch the scene here, NSFW because she's topless.
posted by GaelFC on Jul 10, 2012 - 5 answers