I am in love with my underpants.
Seriously. I learned in one kayak outing that I needed fast-dry shorts, but I was still wearing them over a bathing suit. Once I started looking into sports bras and underpants that might prove suitable for kayaking, I did some research and came across ExOfficio brand.
On the downside, these things are pretty pricey. While small women can get them for as cheap as $15, a plus-sized woman like myself is looking at $20. Yes, for one pair of panties. Still, I took a chance, and I'm glad I did. These things are moisture-wicking, so when I'm just getting sweaty, they keep me very comfortable (which makes them great for cycling, too). But then are almost magically fast-drying! They come in several pretty colors as well, although the selection isn't as good in the plus sizes. I'm now recommending them to friends who play sports and those who do RennFaires and other activities where these "unmentionables" would come in extra handy.