Two: More Shoes

Other than a pair of good, versatile tennis shoes, the only other pair of footwear a person should need is a pair of flip flops. They're light, cheap, easy to clean and dry fast. If it's hot, the showers are gross or if you want to spend a day at the beach, shoes don't quite cut it. Also, if your shoes get wet, it's good to have a backup for the day.