Also known as killer waves or extreme waves, rogue waves are those whose height is more than twice the significant wave height, defined as the mean of the largest third of waves in a wave record.
Rogue waves are natural phenomena that occur most often in deep water and last briefly. Often steep sided with unusually deep troughs, they can present as a wall of water. They can come unexpectedly from directions other than the prevailing pattern of wind and water. These waves are thought to form when individual swells pass through one another and the mass and energy of each wave is added to the sum.
In 2000, a British oceanographic research vessel sailing west of Scotland measured the largest individual wave ever recorded, at 29.1 metres.
The impact of a rogue wave can far exceed the maximum force that a vessel is built to withstand. Ships' bows are ripped open by rogue waves and containers vanish overboard.
A single rogue wave was believed responsible for the sinking of the MS Munchen, a 45,000 tonne cargo ship which went down in December 1978 with no survivors.