I always use the sinus irrigator after I swim in chlorine. I don't feel it so much in open water, but I use it then, too. When I forget (which happens, because I'm human ), I pay for it with sneezing, draining (associated nausea), headaches, and icky sinuses.

Neti pot would work, or maybe a sinus rinse. I use this guy: http://www.hydromedonline.com/hp.html