In the bowl of the food processor, add the parsley, cilantro, garlic, and olive oil. Process for about 20 to 30 seconds, then drizzle in the water or lemon juice. Process for about 15 seconds more.
MARINADE: Rub the marinade over the surface of chicken, fish, or shrimp. Reserve some sauce for dipping when served, and place meat in a plastic bag. Keep refrigerated. Leave the fish or shrimp for about 30 minutes or so, and the chicken for several hours or overnight.
DIPPING SAUCE: Add more olive oil and lemon juice if you want to use it for dipping.