Use a knife and cutting board to carefully cut the watermelon into roughly 1-inch cubes, removing any seeds if present. Measure out 4 cups of the cubed flesh and place it into the blender.
Add 2 tablespoons of honey or simple syrup, 1 tablespoon of freshly squeezed lime juice, and 1 cup of cold water to the blender with the watermelon cubes. Secure the lid tightly.
Blend on high speed for 30-45 seconds until the mixture is smooth and the watermelon is fully broken down, with a slightly frothy appearance on top.
Place a fine-mesh strainer over a large bowl and pour the blended watermelon mixture through it. Use the back of a spoon to gently press and extract as much liquid as possible, leaving behind pulp and solids.
Distribute the strained agua fresca into glasses, adding ice if desired. Optionally, garnish with fresh mint leaves or a lime wedge for presentation. Serve immediately for the freshest flavor and brightness.
