Watermelon is a delicious, healthful choice for summer, and its sweet taste can satisfy any sweet tooth. Watermelon is 92 percent water and has less than 50 calories per cup. It’s a source of vitamin A for eye health and vitamin C for the immune system support. Choose a watermelon without a flat side and that sounds hollow when you knock on it. Look for a melon with a dull (not shiny) rind free of soft spots, gashes or blemishes.