Place watermelon, mint leaves, lime wedges and simple syrup in a tall pitcher.
Using the back of a wooden spoon, muddle the ingredients together helping release juices in the lime and natural oils in the mint.
Add gin and stir.
Fill 4 tall glasses with ice and pour watermelon mixture about 3/4 of the way to the top.
Add a splash of club soda and ginger beer to each glass and stir once.
Check for sweetness - add more simple syrup if needed.
Garnish with extra watermelon, mint and lime to serve.
*Simple syrup is simply equal parts sugar and water heated in pan until sugar dissolves. Store in refrigerator for up to 1 week. Add to lemonade, iced tea or cocktails.**Ginger beer is non-alcoholic. Look for it in any specialty wine or liquor store. Tastes great in a mocktail but also pairs well with gin.***Watching your waistline? Skip the alcohol and add stevia in lieu of simple syrup. Save your calories for the splash of ginger beer. Trust me on this one.