01 - Combine the watermelon, mango, and lime juice in a blender. Blend until completely smooth, ensuring no fruit chunks remain.
02 - Divide the fruit puree evenly among 4 tall glasses, filling each about one-third full.
03 - Pour ½ cup chilled lemon-lime soda into each glass, stirring gently to combine the puree and soda while maintaining some effervescence.
04 - Place a generous scoop of vanilla ice cream on top of each drink, allowing it to float on the surface.
05 - Garnish with fresh mint leaves if desired. Serve immediately with a straw and spoon to enjoy both the drink and melting ice cream.