Pour 1 cup of the water into the blender, then add the cucumbers, avocados, lime juice, honey, 1/4 teaspoon of salt, and the cayenne. Blend until extremely smooth, gradually adding more water until you reach the desired consistency. Taste and adjust the amount of salt, adding as much as 3/4 teaspoon more. Chill for at least 2 hours, then stir in the mint and parsley just before serving.