For centuries mariners have told stories of ships sunk by huge isolated ocean waves, often in perfectly clear weather.

These rogue waves, which appeared without warning, were described as nearly vertical walls of water, up to 100 feet high. These twelve story waves were often preceded by a trough so deep that sailors called it a "hole in the sea."

In the past thirty years evidence has shown that these legendary freak waves really do exist. In 2001, the European Space Agency began using radar satellites to track wave heights across the globe. To their surprise, more than ten separate rogue waves, each more than eighty feet high were recorded in just three weeks.

Several hypotheses exist about the causes of rogue waves. It's possible that something called "constructive interference" creates rogue waves when several waves traveling from different directions in the sea converge in a single spot and add together to form a single extreme wave.

Rogue waves may also occur when storms force waves to travel in the opposite direction of an ocean current. The opposing current acts to compress the waves into a single massive wave.

Now that scientists have discovered that these rogue waves are regular ocean occurrences, it will be valuable to identify the conditions under which they are likely to occur.

In the past twenty years over two-hundred large cargo ships have been lost at sea, many of which may have been sunk by rogue waves. Having proved that these freak waves do exist, scientists are now working to understand all the causes of these waves, with the hope that someday they'll be able to predict them.