01 - Combine cubed watermelon and lime juice in blender. Blend until completely smooth.
02 - Pour puree through fine-mesh sieve into pitcher to remove pulp for smoother texture. This step is optional.
03 - Divide strained watermelon puree evenly among 4 tall glasses.
04 - Place one generous scoop of vanilla ice cream into each glass.
05 - Slowly pour chilled lemon-lime soda over ice cream and puree, allowing foam to rise naturally.
06 - Top with fresh mint leaves and watermelon garnish if desired. Serve immediately with straw and long spoon.