This means that wet hair must be handled much more carefully than dry hair. Alternatively, the chlorine in swimming pool water may have an adverse affect on hair. Chlorine is a strong oxidizing agent and its action on hair may alter both strength and color. Finally, some research in Japan suggests that hair color and quality can change in professional swimmers simply due to the chronic friction between water and the hair cuticle as the individual swims. I suggest one further possibility, that the chlorine may also work on the hair by a physical method rather than having a chemical influence.
Chlorine is a salt in solution.
When you get out of the pool your hair gradually dries out. The chlorine inside the fiber crystallizes. Even though you might shower after a swim, this will only really wash the chlorine off the hair surface and not wash away any chlorine inside the hair fiber itself. To do this you would really have to soak the hair in pure water for a little while. As the crystallization process develops inside the hair, the crystals get bigger and literally push on the inside of the hair fiber.