BOSTON -- Hundreds of beachgoers who were trying to cool off swimming at a Rye, N.H. beach Wednesday ended up stung by a giant jellyfish that lifeguards speared with a pitchfork, sending its still active stingers floating through the water.

They said they thought it was a log.

Nine children who were stung at Wallis Sands State Park were treated at Portsmouth Hospital, authorities said.

"It feels like a big bunch of wasps were swarming on my hand, stinging me," said 7-year-old Pauly Buckles.

His 5-year-old sister also needed medical care.

"She was stung on her chest, her back, her stomach, her face, her hands. Pretty much everywhere," said her mother, Donna Buckles.

"My daughter was screaming. We were trying to figure out what was wrong with her so we picked her up and started to get out of the water and then they started to announce they had caught a jellyfish that had split into pieces and there might be tentacles in the water," said Shannon Kirshenbaum.

The park manager said lifeguards tried to spear the 50-pound jellyfish, which he described as being about 50 pounds and the size of a large turkey platter.

Doug Grout, chief of marine fisheries for the state, said was likely a Lion's Mane jellyfish, a species rarely seen so far south and in shallow waters.

"The jellyfish have nematisists, they're actually like little harpoons that go into your flesh, and even after you get out of the water, because they're so small, you can still have remains of the tentacles on your skin. You're out of the water and you're still being stung," said Steve Spina of the New England Aquarium.

In the northern New England, they average 8 feet in diameter and can have tentacles as long as 150 feet.

Paramedics helped some of the swimmers by applying white vinegar and rinsing of the tentacles.

Lifeguards will keep a look out for any other jellyfish, but the beach was expected to be open Thursday.