Tsunamis are a series of waves caused by a massive disturbance of water. In general, tsunamis are not particularly threatening, as they constantly happen every day around the world, often in the middle of the ocean. In fact, most tsunamis don't reach much higher than regular ocean waves on the beach. But in some cases, the tsunami will develop into potentially destructive waves. If you live in a coastal area, it's imperative that you know what to do should this situation arise.