If everyone is so angry about seat huggers why not just start picking up their towels and tossing them aside? If the person who was reserving the seat is actually using the seat they'll be back in a few minutes or see you from the pool and you can simply apologize and relinquish the chair. Otherwise, its yours for the taking if no one comes to claim it. Or you could just stand there and loudly ask "is anyone really using this chair? anyone?" and if no one responds, take the towel off and set it aside.