Dancers and physicists, gerris or water spiders invented the airboat hydrofoil. You know them well. Small freshwater spiders, gerris glide skillfully over water. They skate on the surface tension of the liquid and defy waves and currents. They are formidable predators. They watch for all the insects, their corpses which drift on the surface. They clean the water film. Physicists have drawn mathematical equations from the sliding of gerris to build hydrofoils. Without biodiversity, no airboat, airplane, or helicopter. Thanks to the gerris, the birds, the dragonflies.