The rescuer, Brandon Quick, told police he saw a group of young men running away, and three teenage girls putting their clothes on, as he arrived home to the apartments early Sunday morning. He said he saw one of the girls push the guard into the pool, and laugh as he flapped his arms up and down and called for help.
The girls then ran away.
Quick pulled the guard out of the water and called authorities. The victim was taken to the hospital, where he was treated and released.
Police say the girls could be arrested on suspicion of assault.
The Associated Press contributed to this story.