Karren Sites of Pittsburgh told Myrtle Beach television station WPDE that she was waist-deep in the ocean with her 8-year-old grandson when a shark approached and bit her arm. She said she pushed the animal away until it released her. She later received hundreds of stitches, she told the TV station.

Sites appears to have been attacked by a medium-sized carcharhinid shark — possibly a bull shark, said Gavin Naylor, director of the Florida Program for Shark Research at the University of Florida, which works with Myrtle Beach to identify marine animal bites. Naylor said he did not have information about the other attack.

U.S. shark mania began with this attack more than a century ago

Although shark attacks often capture public attention, they’re relatively rare. The Florida researchers confirmed 73 unprovoked bites and 39 provoked bites worldwide last year. The United States recorded the most unprovoked bites of any country, with 47, and South Carolina reported four total bites.

Several shark attacks off Long Island, N.Y., last month, including two within two hours, sparked concern as officials said the number of bites might represent a “new normal.” Shark sightings appear to be increasing, possibly as a result of climate change and improved conservation efforts.

Earlier this summer, a Florida teen’s leg was amputated after a shark bit her twice as she was collecting scallops.

Bites are usually a result of a shark mistaking a human for a food source, researchers say. Other times, a shark might be trying to protect its space.

To decrease the already low risk of being bitten, researchers suggest staying with another person, avoiding splashing, staying out of the water during lowlight hours and keeping away from sandbars, steep drop-offs, murky water or people fishing. Slowly leave the water if a shark appears.