Drain pineapple, reserving the juice in a small saucepan. Set pineapple aside. Add enough water to juice to make 1-1/3 cups; bring to a boil. Stir gelatin into boiling juice/water mixture until completely dissolved. Cool in refrigerator for 15-20 minutes or until luke warm. In a mixing bowl, combine whipped topping, pineapple, and cottage cheese. Fold into the gelatin mixture. Pour into serving bowl; chill until set - approximately 30 minutes.