Black belt caterpillar wrestler

Having done some more research on things gven away as promotions I came across the working baking powder submarines that were found inside cornflakes packets.

Happy memories. Do you remember the little diver with a moulding in his back which held a bubble of air? He was exactly weighted so that when you dropped him into a bottle of water, you could make him rise and fall by varying the pressure with your thumb over the top.