Studies have shown that just 2 hours of exposure to the sand at the beach can make you sick. A common sickness people complain about is called gastroenteritis, an upset stomach and bowel. This illness comes from the bacteria the seagulls and marine life leave behind along the waterline. They transfer stomach bugs to humans when wet sand clings to the body. To avoid becoming sick at the beach, set your spot in the sand on dry sand and make sure to rinse off at the beaches showers before going home.