Step 1.
- Cut the watermelon into small chunks and blend until smooth to create fresh watermelon juice.
Step 2.
- Strain the juice through a fine mesh sieve to remove pulp, if desired.
Step 3.
- In a cocktail shaker, combine the fresh watermelon juice, tequila, lime juice, and triple sec.
Step 4.
- Fill the shaker with ice and shake well until chilled.
Step 5.
- Strain the mixture into a salt-rimmed margarita glass filled with ice.
Step 6.
- Garnish with a slice of watermelon on the rim and serve immediately.