@jimjm Thank you! I used light meter app on my iphone, metering on the rock / water area at center for idea of midrange, then checking highlights and shadows to make sure my exposure was centered between them. Scan showed a perfectly centered histogram, which I was happy about.
Very nice! I tried my hand at long exposures (3-4 seconds ) on running water last summer with the Stone Arch bridges in Hillsborough, NH. Something I want to do more of . . Thank you for the inspiration.