you'd be afraid of unless you've done a crime. And you're right, that cop was just doing his job. It happened to some of the people here especially if you're in a such a place where most public don't normally go. I had a Qatari friend who warned us before that cops or CIDs normally patrol routinely in beach areas especially outside Doha proper. Well, there's nothing to be afraid of. Hope you enjoy the morning sun there!