Why don't you sink in the sand at the beach?

You don't sink in the sand at the beach because the sand grains provide enough support and friction to distribute your weight evenly. The sand's structure allows for the spaces between grains to fill with air, creating a solid surface. Additionally, the density of human bodies is less than that of wet sand, further preventing sinking. When the sand is dry, it can become more unstable, but generally, the compactness of the sand keeps you from sinking.