Rogue waves are known as killer waves, and are thought to be just spontaneous large waves that happen in the deep sea. They can be as large as 90 feet but by definition are waves that are three times the average wave height at that particular sea state. They can be deadly even for the biggest ocean liners. They have been seen in the popular TV show, Deadliest Catch, and are known as one of the biggest threats while they are crab fishing. They seem to happen through a combination of high winds and fast currents.