8tbssugar(Adjust to taste and according to the melon's sweetness)
Add the watermelon and water to a blender, working in batches as needed. Cut one of the limes in quarters, and juice one quarter over the blender.
Process until smooth. Transfer to a pitcher and refrigerate, if desired.
To serve, thinly slice the remaining lime quarters, getting about 3 to 5 new slices from each quarter. Place about 3 fresh mint leaves in the bottom of a glass along with a lime slice and 1 tsp to 1 tbs sugar. Muddle to release the lime juices and mint oils. Then top with ice and pour on the watermelon juice.