mystery Waves relaxing on a boat. It's a beautiful lmagine this: You are out at sea, once, No rain is falling, and the winds are calm. All at see something very 1. weird happens. Out of nowhere, you toward you. a wall of water ten stories tall 2. warning This is known as a rogue wave, also called a freak wave. Some people mistake them for tsunamis, but they are 3 increase very different. Tsunamis start out very small in the open ocean, and in speed and height as they get close to the only 4 coast. When a tsunami is coming, the water will often seem to sucked back into the ocean. There is usually no 5 actually before a rogue wave strikes. This kind of wave can appear even in the best of weather. Scientists aren't sure what causes these waves. In fact, as recently as 15 years ago, people thought these waves didn't really exist. But scientists now know they are very real-and very dangerous-even to the largest ships