How do you not make your hair frizzy after its been in the water?

There are a wide variety of anti-frizz serums that will help your hair become less frizzy. You can also think about buying shampoo and conditioner that fights frizz.

But, for on-the-spot relief of frizz, I would suggest pulling your hair into a ponytail (if you can) or trying to manually flatten your hair. If that doesn't work, sometimes actually dampening your hair reduces frizz. But, whatever you do, don't brush your hair. It just adds more static and frizz into your hair.