Thanks for your question. A lot of people wonder about sperm in pools. Sperm can live outside of the body for a short amount of time, except in very specific conditions. Good news is that sperm does not live long in pool water for a bunch of reasons, including the water itself and the temperature. So, you do not have to worry about girls getting pregnant from swimming in pool water that may have sperm in it.
It is very important to know that if you have vagina-penis sex in a pool, a girl can still get pregnant.