REMOVE seeds from melon halves; cut thin slice from bottom of each half. Scoop out melon flesh, leaving 1-inch-thick shells. Place upside-down on paper towels to drain.
ADD boiling water to gelatin mix; stir 2 min. until completely dissolved. Stir in cold water. Refrigerate 15 min. or until slightly thickened. Pour into melon shells.
REFRIGERATE 3 hours or until gelatin is set. Cut into wedges.