“We’re still looking for a pattern,” he said. “I am going to be talking to my secretary of public safety to see if there is any one-fit-all approach to dealing with this issue. I doubt there is because each circumstance is so different.”

As much of the country heads to be beach for the long July 4 weekend, swimmers could be forgiven for peering into murky water for a fleeting shadow or a fin jutting out of the depths. But should they worry?

“The ‘summer of the shark’ tends to be media driven,” said Gregory Skomal, a senior marine fisheries scientist in Massachusetts. “Once people get sharks on the brain, these attacks will do that. People start to see them everywhere.”

Noting that 2015 marks the 40th anniversary of the classic shark movie “Jaws,” Mr. Skomal said perceptions of danger are fueled by the proliferation of social media, cellphone cameras and GoPro devices, such as one used to record a great white shark off Jones Beach, on Long Island, in June.

Scientists rely on long-term data to determine if the beaches are more dangerous this year than in previous years. But swimmers — and parents — don’t have that luxury. Even Mr. Skomal admits the frequency of reported shark bites in North Carolina has been “unusual.”