Cayo Arena, a tiny island paradise in the Dominican Republic, is mainly used for snorkeling and diving in its incredible, colorful coral reef. The sand and water are so beautiful that you'll feel like you're in a postcard. The water is easy to enter, with calm waters and a sandy bottom. The ocean is usually very calm, making it easy to relax in the water. The beach can get crowded, so it's suggested to visit during off-peak season and early in the morning.