I use skincueticals sunblock, recomended by my dermatologist. It is UVA/UVB rated with a higher blocking additive than what you can get over the counter. I get skin cancers cut off every 6 months, but I catch the differences in freckles very quickly, so the area removed is very small. (sooner gone, smaller scar)
I constantly re-apply, wear good fishing shirts, and finally found a cap with wide brimmed bill and neck flap.