Slice the watermelon and remove the skin. Place the watermelon chunks in a blender jar and blend until no chunks remain. (Depending on the size of your blender, you may need to do this in batches.) Pour the watermelon juice through a strainer to remove pulp and and lone seeds. This can be done up to 2 days ahead, store in an airtight container in the refrigerator.
Pour 3 cups of watermelon juice into a large pitcher. If you have leftover juice, freeze it in ice cube trays or ziploc bags to use later.
Add vodka, midori, lime juice, and wine to the pitcher. Stir.
Serve over ice garnished with watermelon slices and limes.