To keep it simple, you can start with store-bought limeade, says chef Karen Hatfield of Odys + Penelope and Sycamore Kitchen restaurants in Los Angeles.
In a large pitcher (at least 2 1/2 qt.) stir mint, lime, and 2 cups cold water with a wooden spoon to release flavors. Stir in limeade, watermelon, and 2 cups ice cubes.
Odys + Penelope and The Sycamore Kitchen restaurants, Los Angeles