In the popular imagination, they have the qualities of a movie behemoth--surging, Jaws-like, out of nowhere on a sunny afternoon to gulp down party boats full of fishermen out for an afternoon of sport.
They have been implicated in the demise of oil tankers. They have been blamed for drowning tourists and capsizing data buoys. They have been accused of ripping the railings off an Italian ocean liner and almost sinking the Queen Mary.
They are rogue waves.
"When people say a 'rogue wave,' I have this image in my mind of some guy on Mt. Olympus creating a wave and turning it loose," said Steve Elgar, an oceanographer at Washington State University. "Clearly, that's not what's happening. So we try to figure it out."
But so far, the scientists' figurings have been far from conclusive.
Most agree that a rogue wave is a rare coincidence of many smaller waves, perhaps from different storms, moving across the ocean. They converge, but instead of canceling each other out, they form a single wave of extraordinary size.
But beyond that, there is little consensus.
Some scientists believe rogue waves travel alone. Others say they move in twos and threes. Some Say they occur in storms, outside of storms, only in deep water, only in shallows. Some say they have a distinctive shape and travel at odd angles.
A few oceanographers suggest that rogue waves are not even "roguish." That is, there is nothing truly aberrant about them. They say if you wait long enough, one will come along--like the statistical chance of flipping a coin 10 times and coming up with 10 heads.
Others insist that they are genuine freaks. In a stormy sea, they say, statistical probability and mathematical predictions fall apart. Out on the ocean, extraordinary waves occur that no mathematician would be able to predict.
"Research on this particular phenomenon is very spotty," said Frank Gonzalez of the National Oceanic and Atmospheric Administration. "Part of it is that in fact, it's a very rare event. And you're hard pressed to gather enough dependable observations."
Yet the proliferation of commercial shipping and recreational boating has created a new demand for reliable data about rogue waves. In light of the environmental and economic consequences of, say, an oil tanker's sinking, some scientists say more work must be done.
"Certainly, there has got to be some sort of educational program," said Richard Seymour of Scripps Institution of Oceanography at the University of California, San Diego. "At least something that says, 'Waves are variable, guys. Don't relax just because you don't see any big waves now.' "
First, a few facts about ocean waves:
Most ocean waves are caused by wind. The air moving against the water initially creates ripples. Then the wind begins to press against the sides of the ripples, transferring energy from the air to the water and producing waves.
Waves, rogue or not, can grow to remarkable heights. Sailors say 45-footers are common in North Atlantic storms. Others have reported 75- and 90-foot waves. In one famous account, a Navy officer crossing the Pacific in 1933 reported a wave estimated at 112 feet.
"Think about what it means for a 10-story wall of water to be coming onto your face," marveled Robert Guza, a wave specialist at Scripps. "I mean, big waves get big, and they don't need to be rogues."
Nevertheless, the literature is filled with anecdotal accounts of so-called rogue waves.
In 1942, when the passenger liner Queen Mary was serving as a troop ship, she was struck broadside in a gale 700 miles off Scotland. An eyewitness was quoted as saying the ship "listed until her upper decks were awash," then righted herself.
In 1966, accounts state that a huge solitary wave in a storm swamped the upper deck of an Italian liner 800 miles off New York. The wave reportedly smashed windows 80 feet above the water line and ripped off steel railings on the upper deck.
Earlier this year, 10 people drowned off Baja California when a San Diego sportfishing boat was suddenly swamped and sunk. The two survivors of the Feb. 5 accident on the Fish-n-Fool said the boat was capsized by a sudden 20-foot-high wave.
Oceanographers say not all rogue wave stories are true.
"Well, it's a hell of a convenient way if you've been careless at sea to explain it," said William Van Dorn, a research oceanographer emeritus at Scripps who has served as an expert witness in marine casualty cases. "Very often, you can see through the arguments, that the guy was careless or negligent and let himself get in a bad situation."
Some reports of extreme waves are more easily explained than others.
Local topography is known to affect wave height in shallower water, said Richard Seymour, head of the ocean engineering research group at Scripps. If a wave encounters a sudden shoal or a current, it may suddenly rise to an unusual height.