In a cocktail shaker, muddle the mint leaves. Add the blueberries and muddle again until fully smashed. Add the rum, lime juice and simple syrup and fill the cocktail shaker with ice. Shake until cold.
Place ice into a glass, and strain in the liquid. Top off the glass with soda water. Garnish with additional mint leaves, lime wedges, and blueberries.
Notes
*To convert to tablespoons, 1 ounce = 2 tablespoons