Step 1Combine the honeydew and cold water in batches in a blender and blend until smooth, pouring the puree into a pitcher as each batch is blended.
Step 2To the last batch of pureeing mixture, add the serrano chile, lime juice, simple syrup and cilantro leaves, pulsing until leaves are tiny flecks.
Step 3Blend in the tequila. Pour into the pitcher and stir in ice cubes.
Step 4Garnish the pitcher with a few sprigs of cilantro and two or three red chile peppers.