In a blender, combine the cubed watermelon, cold water, and honey. Blend until smooth.

Strain the mixture through a fine mesh strainer into a pitcher to remove pulp.

In a small saucepan, bring a cup of water to a boil. Remove from heat and add the rosemary sprigs.

Let the rosemary steep for about 10 minutes, then remove the sprigs and add the rosemary-infused water to the watermelon juice.

Stir in the lemon juice.

Pour the cooler into glasses filled with ice.

Garnish with lemon slices, watermelon slices, and additional rosemary sprigs.