More than 300 thousands people were killed or missed by the great tsunami wave due to the Off Sumatra Island earthquake 2004.12.26. Many disaster processes were recorded by many video cameras which were very popular world wide. It is disclosed by these videos that tsunami wave is not a usual big sea wave, but a big sea stream or flood. Water itself flows very fast. Therefore, people can not survive against even the tsunami 50cm deep. People should refuges to a safer place immediately after they feel a strong earthquake in the coastal area. The higher, the safer against the tsunami. The safer place is a higher place such as a top of the hill, higher floors of a reinforced concrete building, etc.