A water strider stands on a pond surface without sinking, dimpling the film slightly beneath each leg. Which explanation accounts for this feat?

Core Concept

Molecules at the surface have no water neighbors above them, so the unbalanced attractions pull them inward and place the interface under constant tension. This tension behaves like a stretchable skin able to bear light loads. The strider distributes its weight across long legs tipped with water-repellent hairs that avoid piercing the film, so it depresses rather than ruptures the surface. Any contaminant that disrupts hydrogen bonding, such as soap, collapses the tension and the insect sinks.