Last summer I was not prepared and one month of unpreparedness out here made a mark on my melasma, so I learned quick!
1. Elta MD Sport has the Skin Cancer Foundation endorsement, will not sting your eyes if you are sweating and has a pretty good feel for being sweat/water resistant. It is also oil free and paraben free! Bonus!!
2. Phloretin CF- AMAZING!!!!!!!!!!!!!!!!!!!!!!!!! Goes under sunscreen and gives you so much more protection than sunscreen alone, I never leave home without it (unless it's night, of course). CE Ferulic is also fantastic, but is for drier skin. These two skinceuticals products are the best antioxidants for summer sun, in my personal opinion. :)
4. Colorescience Sunforgettable Mineral Sunscreen is also amazing! It is an spf 50 and is a brush and spf combined in one clever brush. I cannot lie, I do put both on top of my sunscreen when in the sun for long periods of time, but if that's not for you than this is a great way to be able to reapply throughout the day with no hassle.