That happens to me all of the time, I usually take extra care when drying myself and my hair to make sure I am not still wet and I take a coat and thick clothes just to make sure I don't get a cold.
Getting 'a cold' and getting cold are two different things. A cold is caused by a virus. Getting cold is caused by being exposed to water or air at a chilly temp. If you're swimming in a chlorinated pool, I doubt it's a virus. Most likely the chemicals in the water are agitating your sinus. Next time you go, don't put your head under water and see what happens. If you don't get the same reaction most likely, that's what it is.
no its because after you get out of the pool your cold and you go to a really warm place to try get warm cold and hot do not mix and concidering we are warm blooded over doing it causes motion sickness and to be cold at the same time turns it into a cold sickness and that is how you get a cold from after swiming in a pool