A diagram of a leg of a water strider on the water surface is shown. A small gap is present between the leg and the water surface. There is a small depression in the water surface at the point where the leg is above the water surface. Space-filling models representing water molecules are present just below the water surface at the point where the leg is positioned. Water molecules are connected to each other by dotted lines representing hydrogen bonds. An inset of a photograph of a water strider resting on water is also shown.
The cohesion of water creates a force called surface tension that resists the entry of water-repellent objects such as this water strider. To overcome surface tension, a nonpolar object must push hard enough to break many hydrogen bonds. Water striders don't weigh enough to exert such force. This means little to us, but it can be vital to a tiny insect.