In large bowl, dump the contents of the pineapples and pudding mix allow to set for 5 minutes.

Add the marshmallows, coconut and walnuts to the mixture and mix well. If you let the coconut and marshmallows dry out, it will help absorb the juice from the pineapples.

Add cool whip and mix well.

Place in a container with a lid.

Chill for about 1 to 2 hours. For best results, allow to set overnight.