I find that free-flowing skirts, dresses, blouses, and the like are just as cool as a tank and shorts. They also provide more sun protection.
Even on hot days at the pool or lake, as soon as I'm out of the water, I put on a long-sleeved cover-up, sunglasses, and a straw hat. I find that blocking the sun is better than baring the skin.
REI and other outdoor clothing providers have different styles that will help keep you cool and provide protection from the sun, ticks, and wandering eyes... ;)