I finally figured out the location of that beach in the first scenes of Cosmos!
It’s somewhere in California, about a hundred miles south of San Francisco, 14 miles south of Monterey. The exact coordinates of the place Sagan/Tyson stood are, more or less:
I don’t even know if anybody else cares about this, and I’m sure there are plenty of people who know already, but I’ve always wanted to know and could never find it through basic Google searches. I only found it after searching the California coastline in Google Earth until I found a place that matched the first scene in the new Cosmos.