In the locker Sam noticed that he had grabbed the wrong bag. Instead of his trunks he found one of his sister Rebecca's bikinis in the bag.
He considered what to do and made up his mind to return home in order to collect his swimwear.
The only thing that annoyed him was that he had paid the entrance fee just for nothing.
He got dressed again, took his bag and left the locker. He had already made half the way to the exit when he noticed that he had left his sister's bikini in the locker. At first he thought why not leaving that damn thing behind as it caused him to leave the beach without going to the water. Then he remebered how wild Rebecca could become when she misses something. And this bikini was not only "something" but her favourite one.
So Sam turned back to collect the bikini.