You'll want to serve Watermelon Margarita Pops with a side of sea salt for sprinkling on top, but be careful! You'll have to slurp it up before the ice melts.
Grate zest from 1 lime to equal 1 tsp. Squeeze juice from limes to equal 1/2 cup. Process lime juice and watermelon in a blender until smooth. Pour through a fine wire-mesh strainer into a large measuring cup, discarding solids. Stir in tequila, sugar, and 1 tsp. lime zest, stirring until sugar dissolves. Pour mixture into paper cups.
Cover each cup with aluminum foil; make a small slit in center, and insert 1 ice-cream spoon into each cup. Freeze 8 hours or until firm.