prepare jello according to package. set aside to cool (dont refrigerate yet)
once jello has cooled completely stir in pineapples and sliced bananas and mix well then chill.
using a sauce pan, drain pineapples as much as you can into pan, add corn starch and sugar cook till it thickens, and chill. once chilled mix the cool whip into this mixture and chill till jello is set.
spread cool whip mixture on top of jello and sprinkle coconut on top and enjoy!