water socks are those rubber shoes that you can wear in the pools and around water parks without having to take them off anytime.
They are not expensive and my advice is get a pair if you plan on going to public pools, my DD got a plantar wart and they are a pain to get ridd of , you can buy them in Wal-mart, K-mart or Target, they are in the shoes department usually.
We always bring a pair into the parks too for when DD wants to play in fountain/wet areas. I like having something on her feet when she's running around. We always get ours at Target, I got some at Wal-mart once and the color ran onto her feet and they fell apart after a couple of weeks.