Found this on the Kitchn today:
Refreshing Summer Recipe: Aguas Frescas | Apartment Therapy The Kitchn
Watermelon-Lime Agua Fresca
serves 4 (fills one blender)
2 pounds seedless watermelon (1/8th of a good-size watermelon)
1 cup cold water
2 teaspoons lime juice
1 tablespoon simple syrup or agave nectar
Honeydew-Basil Agua Fresca
serves 4
1 honeydew
2 cups cold water
4 teaspoons lime juice
2 tablespoons basil-infused simple syrup or agave nectar
For the simple syrup: Mix 1/4 cup water with 1/4 cup sugar. Bring to boil over medium-low heat and simmer, without stirring, until all sugar is dissolved (about three minutes). Remove from heat, add 1 tablespoon chopped fresh herbs (I used lemon basil for its fantastic citrus scent, but you could also use regular basil or mint). Let steep for 15 minutes until flavor has infused the syrup.
Blend all ingredients, adjusting sweetness as needed. Strain through a mesh strainer or cheesecloth (optional). Serve over ice.