Cut the watermelon in half lengthwise and scoop out the flesh into chunks, removing as many seeds as you can, then cut the chunks into roughly 2-inch pieces.

Place the watermelon chunks into the blender, filling it about halfway to allow room for blending.

Pour in the cold water and add the granulated sugar and pinch of sea salt.

Blend on high speed for 1 to 2 minutes until completely smooth and no chunks remain.

While blending, add the fresh lime juice through the blender lid to incorporate evenly.

Pour the blended mixture through a fine mesh strainer lined with cheesecloth into a large pitcher, pressing gently with a spoon to extract all liquid.

Taste the agua de sandia and adjust by adding more lime juice, sugar, or water to achieve a balanced flavor.

Chill in the refrigerator or pour over ice and serve immediately for best refreshment.