Flying fish taxiing on the water's surface

Flying fish is a fascinating creature which is known for their locomotion between water and air. Flying fish walk on the water's surface with their tails slapping the water surface at high frequency. This behavior is the so-called taxiing. By taxiing, flying fish propel themselves above water and re-initiate gliding. Previous researchers have studied western grebes and basilisk lizards walking on the water surface by slapping the water surface [1,2], but the working principle for flying fish taxiing remains unknown. In this study, we investigate the tail-slapping frequency of flying fish experimentally and theoretically. Flying fish beat their tails on the water's surface at a frequency of 13.5 Hz, which is higher than most other water-walking animals. With the force analysis, we predict that the minimum tail beat force to sustain a 200-g flying fish's locomotion above the water surface is around 2 newtons. This study will contribute to the mechanics of taxiing and advance the design of hydro-aero robots.