Roughly chop and deseed watermelon. You should have about 12 cups of chopped fruit. Reserve two cups. Puree 10 cups watermelon and cranberry juice in blender. Strain pureed mixture through a fine sieve into a large bowl or plastic container; discard pulp.
Peel, seed and small-dice cucumbers and apples, deseed and dice red bell peppers and peel and small-dice red onion. Pick and chop mint and parsley, set aside for garnish. Seed, de-vein and finely chop jalapeno pepper. Combine cucumbers, apples, celery, bell peppers, onion, herbs, limejuice, vinegar and jalapeno with the watermelon-cranberry liquid and stir to combine. Finely chop the reserved two cups watermelon and add to mixture. Salt to taste.
Cover and refrigerate until well chilled (an hour minimum). Garnish with the chopped mint and parsley and serve well chilled.