Heat oven to 350. Grease bottom only of 13x9 inch pan.
In large bowl, beat cake mix, water, oil, eggs and mashed bananas with electric mixer on low speed for 30 seconds, then on medium speed for 2 minutes, scraping bol occasinally. Pour into prepared pan.
Bake 33-38 minutes, or until toothpick inserted in center comes out clean. Cool completely, about 1 hour.
Poke top of cake every 1/2 inch with long-tined fork, wiping fork occasionally to reduce sticking.
In large bowl, stir together condensed milk, coconut milk and whipping cream. Carefully pour evenly over top of cake. Cover and refrigerate at least 8-12 hours, or better overnight. It lets the mixture soak into the cake.
Toast a handful (or more)of coconut, and sprinkled all over the cake covering it well.