An observation of bottom impact phenomena on a flat bottomed ship has been made by means of a high speed video recording system and the transparent model of a tanker. The model was towed in regular waves while making pitching and heaving motions freely. Two video cameras were used in the experiments. One camera was set to take a picture of bottom impact through the transparent hull and the other camera was used to record the impact pressure in an oscilloscope. Both pictures were superimposed for synchronism between pressure fluctuation and the sequence of events. Three kinds of impact phenomena were observed during the experiments. One was oblique impact, another was trapped air impact and the other one was normal impact. The video shows that the high peaked pressure in the wide area appears in the case of trapped air impact while the pressure gauge is in the trapped air and the so called vibration of compressed air follows. The normal impact which is characterized by earlier touching of the forepart of the bottom were examined to show that its high pressure are related to the rapid expansion of the wetted area. Discussion are also made on the possibility of coexistence of trapped air and the normal impacts, based on the experimental results. The correspondence of the events to the pressure fluctuation were examined to show that the oblique impact could be explained by the estimation by one of authors. In every cases it is seen that the three-dimensionality plays important role in the bottom impact phenomena.