Measure and chop the watermelon into small chunks, removing any seeds if present.
Add the watermelon chunks to a blender and blend until smooth and vibrant in color, about 30 seconds. The mixture should be even with no large fruit pieces remaining.
Pour the watermelon puree into a cocktail shaker through a strainer to catch any pulp, filling it about halfway.
Add the tequila, lime juice, and honey to the shaker. Fill with ice, then secure the lid and shake vigorously for about 15 seconds until well chilled and mixed, hearing a consistent shivering sound.
Remove the shaker’s lid, strain the mixture into a chilled glass, and observe the bright pinkish-red hue with a slightly foamy top. Garnish with a small watermelon wedge if desired.