Add all the ingredients in a blender. Blend until all the ingredients are totally pulverized, should take about a minute. Serve with a squeeze of fresh lime.
Depending on the watermelon you have sometimes the juice can be a bit pulpier. If you do not like pulpy texture, blend it again for another minute by adding an extra half a cup of chilled water or go ahead and strain the juice.
You may want to stir the juice with a spoon if it starts to separate over time.
Go ahead and add a splash of rum, or stir in vodka and triple sec for a fun cocktail.