Step 1

Combine the watermelon, cucumber, lime juice, salt, and mint in a blender and blend until smooth.

Step 2

Strain the mixture through a fine-mesh sieve, pressing to release all the liquid.

Step 3

Into a tall glass filled with ice, pour 1/2 cup of the watermelon mixture and top with 1/2 cup or more of the sparkling water. Stir in agave to taste, if using.

Step 4

Slip slowly until you've recovered. Have another glass if you need it. Store any remaining cooler covered in the refrigerator for up to 1 day. Stir well before drinking.