Watermelon is mostly water, making it a hydrating and refreshing choice, especially important during hot weather or when trying to increase your fluid intake. In fact, watermelon gets its name from its high water content, which can be up to 92% by weight. Watermelon is a rich source of lycopene, an antioxidant that may help protect against heart disease, cancer, and other chronic diseases. It is also a good source of Vitamins A & C, as well as potassium and magnesium.