Penguins are wing-propelled diving birds living in the South Hemisphere. Previous biologging studies have revealed the basic swimming abilities of the penguins, such as descending speed and diving depth, under wild condition. However, little study has been done on the biomechanics of the flapping-wing diving of the penguin. In particular, 3-D wing kinematics and body motions have never been measured so far. Hence the hydrodynamic mechanism of the instantons agile maneuver of diving penguins is totally unknown. In this paper, we recorded a diving penguin in a large water tank at an aquarium with multiple commercial waterproof high-speed video cameras. Based on the obtained images, the wing and body motions were three-dimensionally reconstructed. The preliminary results demonstrated that the diving penguin generated the hydrodynamic force during upstroke rather than during downstroke unlike flying birds in the air.