Prepare the Watermelon Juice: Start by blending the diced watermelon in a blender until smooth. Then strain it through a fine-mesh sieve to remove any pulp, leaving you with fresh watermelon juice.

Muddle the Mint: In a cocktail shaker, add the fresh mint leaves and muddle them gently. This will release their flavor without breaking them apart too much.

Combine Ingredients: Pour the Bacardi Superior Rum, fresh watermelon juice, lime juice, and simple syrup into the shaker with the mint. Add a handful of ice cubes.

Shake: Secure the lid on the shaker and give it a good shake for about 10-15 seconds, until the mixture is well-chilled.

Strain and Serve: Strain the cocktail into a tall glass filled with ice.

Garnish: Garnish with a slice of fresh watermelon and a sprig of mint for a finishing touch.

Enjoy: Serve immediately and enjoy your refreshing Bacardi Watermelon Cooler!