"Strange" spike in shark attacks puzzles experts

MIAMI -- Andrew Costello was attacked by a shark Wednesday in North Carolina, becoming the eleventh person to be bitten by a shark since mid-May.

A 68-year-old man, named Andrew Costello, was attacked by a shark in waist-deep water off Ocracoke Island, North Carolina, July 1, 2015. He was swimming directly in front of the lifeguard stand, about 30 feet offshore. Laura I. Hefty/AP

Costello, 67, suffered wounds to his rib cage, lower leg and hip. He was waist deep about 30 feet offshore near Ocracoke Island when the 6 to 7 foot shark pulled him under.

Costello, the former editor of the Boston Herald, was airlifted to an area hospital, where he is listed as being in good condition.

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The recent spate of shark attacks has left many beachgoers nervous.

Dr. Samuel Gruber, the director of the Bimini SharkLab research facility in the Bahamas, says the spike in attacks suggests something strange is going on.

"The trend is normally zero or one attack in that area in any one year," said Gruber.

Theories as to why this is happening range from time of day, to bait fishing, sea turtle migration, lunar cycles and global warming.

Gruber says there are more than 500 kinds of sharks inhabiting every marine environment and freshwater too.

"There are some sharks that are highly coastal that will swim right up on the beach," he said. "They'll even chase fish out on the beach out of the water to get the fish."

The data we do have is based on human, not shark behavior.

"People swim in warm waters like Florida and so you have more people in the water with sharks you're likely to get more shark attacks," said Gruber.

The Florida Museum of Natural Science says your chance of being bitten by a shark are 1 in 11.5 million, still the National Park Service has sent out a shark warning telling people to stay close to the shore and in small groups.