An aquarium filled with water has a yellow powder on the surface. On the bottom of the aquarium is a chain. The challenge is to pick up the chain with your hand, but your hand has to remain dry.
How does it work?
The solution is just to grab the chain and pull it out of the water. The layer of Lycopodium (the so-called "yellow powder") that is spread on the surface of the water will cover the hand like a waterproof glove. The Lycopodium produces a rough microscopic surface that is water-resistant; meaning the powder keeps the water and the hand separate, and the hand remains dry.
