June is a perfect time for the Waterloo, named after the Battle of Waterloo. The famed battle was fought on Sunday, 18 June 1815, near Waterloo in present-day Belgium, then part of the United Kingdom of the Netherlands.
Muddle the watermelon and simple syrup in the bottom of a mixing glass until the all the fruit has turned into a juice.
Then add the rest of the ingredients, fill up with 5 large, cold ice cubes.
Shake briefly, and pour all unstrained back into a tall Collins glass.
Garnish with a piece of watermelon with rind.