This light, refreshing drink popularized in Mexico is a terrific thirst quencher on a hot summer day. The trick with making agua fresca (Spanish for "fresh water") is to infuse the water with fruit essence without turning it into a smoothie or slushy drink. Feel free to experiment with other flavors such as strawberry, mango, cantaloupe and honeydew.
Cut the watermelon flesh from the rind. In a blender, process half the watermelon pieces with 1 cup of water until smooth. Pour through a strainer into a pitcher. Repeat the process with the remaining melon and water. You should end up with about 8 cups of juice. Stir in the lime juice and agave. Pour into ice-filled glasses and garnish with lime slices and mint.