Why do a person go down in quicksand?

A person sinks in quicksand due to its unique properties as a non-Newtonian fluid, which means its viscosity changes under stress. When someone steps into quicksand, their weight displaces the water and sand mixture, creating a dense, unstable environment. As they struggle, their movements can further decrease the viscosity, causing them to sink deeper. Additionally, quicksand typically forms in areas with high moisture content, making it difficult to escape without external assistance.