This depends a lot on your tolerance to UV. Do you burn easily? I don't, so take my responses from that perspective.
I've lately had good luck with lightweight synthetic fiber "outdoor" wear that is designed to dry quickly. The idea is, if you get wet, it dries fast. And if you need to hand wash it underway, etc. ExOfficio.com has a number of items in this category, although they are a bit on the pricy side. I'm sure there are a number of others. REI may be a good source.
The issue with cotton is two-fold. First, if it gets wet, it looses its insulating capabilities. This is less important in warm latitudes, but is the reason wool is recommended over cotton for cold-weather outdoor use. Second, once it gets wet, it takes a long time to dry. This is important anywhere, and is where some of the nylon or other synthetics shine. If you wash a pair of jean and clip it to your lifelines to dry, it will probably still be wet the next day.
s/v Dancing Days
Lewisville Lake, TX