Lorna, your naive sexpot on Baywatch sounds exactly like the kind of renewable-virgin role I had in mind. USA network is rerunning that show, so I watched four episodes this week. There were three blonds bouncing around, but they were named C.J., Donna, and Neely. No Dawn or Summer.
There were also two dark-haired lifeguards. One was Alexandra Paul ("Stephanie"), whom I remember from a couple of Perry Mason movies only because of her last name. And the other was Yasmine Bleeth ("Caroline"), who I suspect had stopped looking naive by the time she was three years old.
So I don't think I saw the one you were talking about.