Using food as a platter or bowl to serve food in is a genius idea. Because once you're done digging into the fruit salad inside this watermelon, you can then eat the "bowl"! Well, maybe not the rind. But you get the point.
Take a gander at this food tutorial to learn hwo to carve a bowl with jagged edges out of a watermelon. Then toss pieces of the watermelon into the salad to really make use of all your resources!