To make the mint simple syrup, add the water, sugar and fresh mint leaves to a saucepan and heat over medium heat. Whisk constantly until the sugar dissolves and the mixture comes to a boil. Let it bubble for a minute or so, then reduce the heat and let it cool completely. If I make it before, I’ll usually put it in a bowl or jar, let it come to room temperature then stick it in the fridge overnight. I do like to let it cool completely before adding it to the blender. This will make extra, so you can store it in the fridge. You can use it in coffee or cocktails!

Make sure to freeze the watermelon cubes for at least 6 hours, or even overnight.

Combine the watermelon cubes, rum, lime juice and mint syrup in a high powered blender. Blend until combined. Add in the seltzer and blend again. Taste and if you would like it to be sweeter, add more mint syrup.

Pour in a frosted glass and garnish with fresh mint and lime wedges.