I wore my orange frayday t-shirt while swimming. Although a rabid swimmer, I still have not gotten a sunburn in the last 10 years (at least!). The secret: Lots of suntan lotion and wearing a t-shirt while swimming until 2:00Pm or 3:00 PM.
I arrived at Hamilton Pool early one Monday morning. Indeed, for an hour or so I was the only visitor there and had the lake all for myself (horray for vacation days!)