No matter how much warning officials give, some people flock to the shore to see waves from hurricanes. The ocean, however, is not always as predictable as people might like.

Though Hurricane Bill did not make a direct hit on the U.S. East Coast, its wave-making power was made clear Sunday when a surprisingly large wave, termed a "rogue wave" by the Portland Press Herald, struck Acadia National Park. A 7-year-old girl was killed, and three other people had to be pulled from the water.

Scientists don't fully understand how unusually large waves can suddenly emerge among smaller ones. But a study last year revealed one way:

Normally a large wave on the open ocean breaks into smaller waves, in a dampening effect caused by interaction with other waves. But lab tests showed that the opposite can occur: Small waves can join forces to become monsters "that emerge surprisingly quickly," explained researcher Peter McClintock, a physicist at the University of Lancaster in England.

Sunday's killer wave got an assist from an above-average high tide and Hurricane Bill's storm surge, which piled water near the coast to put otherwise high-and-dry locations at risk. How exactly the surprisingly large wave formed remains unknown, however.

Interestingly, a series of mysterious, 12-foot waves — which had the look of tsunami waves — struck Maine's Boothbay Harbor last October.

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