Head lice are unlikely to be spread through the use of swimming pools. Head lice survive by holding onto hair and, although pool chlorine levels do not kill lice, the lice are not likely to let go when a person's head goes under water.
Head lice can be spread by sharing towels or other items that have been in contact with an infected person's hair. To protect yourself from head lice at the pool, do not share towels, hair brushes, or other items that come into contact with someone else’s hair. If you already have lice, do not swim or wash your hair within 1–2 days of treating it with anti-lice shampoo — these actions will make the treatment less effective.
For more information on head lice, please visit CDC's Head Lice page.