DRAIN pineapple, reserving juice. Add cold water to juice to measure 2 cups; set aside.
STIR boiling water into gelatin in large bowl at least 2 minutes until completely dissolved. Stir in measured liquid. Refrigerate about 1 1/2 hours or until thickened (spoon drawn through leaves definite impression). Stir in pineapple chunks and oranges. Spoon into 6-cup serving bowl.
REFRIGERATE 4 hours or until firm. Garnish as desired. Store leftover gelatin in refrigerator.