In the popular "Poseidon Adventure" movies, a cruise ship is overturned and capsized when it is unable to turn fast enough to meet a rogue wave head on. The original movie wave was 50 feet high, which became higher in every new remake until the 2006 "Poseidon" made it 200 feet high. Although these kinds of rogue waves were long thought to be nothing more than a tall tale fit for disaster movies, dedicated studies from satellites and radar data from offshore oil platforms have confirmed the existence of rogue waves.
Rogue waves are extremely high, isolated waves which seem to come out of nowhere. Most documented rogue waves are higher than 90 feet, with all the surrounding waves much less than half that. Some are up to 100 feet high.
Even higher waves may well be possible, but few ships can survive them to report them. Most modern ocean equipment, from container ships to oil platforms, is designed to withstand a maximum of 30-foot waves. It is now believed that at least some of the 20 supertankers and container ships which go missing in an average year due to severe weather were the victims of rogue waves.
Ocean waves can be reinforced by other waves which interact with them, with crests adding to crests and troughs canceling out crests. The final height of an ocean wave on the open sea is the sum of all the wave heights at that spot. Once in a while, all the crests come together just right so that there is little or no cancelation by a wave trough. This is the rogue wave.
A rogue wave can occur anywhere in the open sea. There doesn't have to be a nearby storm to produce unusually high waves, although it doesn't hurt. Rogue waves are most likely to be encountered close to the leading edge of storm fronts or in places where normal waves, storm-tossed or otherwise, meet strong ocean currents or eddies.
Rogue waves are surprisingly common. In a single 3-week period, satellites confirmed the existence of 10 rogue waves around the world which were more than 90 feet high. Further research on rogue waves is ongoing.
The third (2006) version of the movie changed the original novel concept of a mid-ocean tsunami to a true rogue wave. This was an accurate change. On the open ocean, even the strongest tsunamis are only a few inches high. They only grow in height when they reach shallow or otherwise enclosed water, which forces the wave energy upwards. Thus, a rogue wave cannot be caused by an undersea earthquake, because rogue waves only occur on the open sea.