premise: a snowboarder balancing on his hand with the snowboard in the air. hypothesis: A snowboarder is in the snow.
entailment: To say the snowboarder is balancing on his hand with the snowboard in the air implies that he is not standing on the snowboard, as if he's fallen over and, and so is in the snow. If he is balancing on his hand he is balancing against something and the only thing that comes to mind is snow.