"We thought he was joking until he went under," Boone said.
So Boone immediately jumped in after his friend, he said. But when he got out to the middle of the river, the water was too deep for him to stand, he said.
"I kept going underneath the water and tried to push him up," he said. "But he wouldn't go. I tried to do my best."
Meanwhile, the other children began screaming for help.
David Smith, who lives nearby, said he heard the screams and ran down to see the boy's head bobbing up and down in the water.
"I just got rid of my shirt, shoes, hat and wallet and jumped in after him," said Smith, 38. "I snatched him up and brought him up on the bank."
Smith said neighbors covered him with a blanket and tried to help him breathe. Initially, the boy spit out water and complained of not being able to see.
"He was just exhausted," Smith said.
Tabitha Wise, who lives along the river, said she saw the incident from her second-story balcony. At first, she said, she thought the children were playing. But when she heard the screams for help she called 911 and ran down toward the river.
"You saw the boy one minute and the next he's underwater," Wise said. "All you could see were the bubbles."
The grandfather of Wise's children also jumped in the water in a rescue bid. But Ed Carrie said he was too far upstream to find the boy.
"He'd been under the water for quite awhile before I saw him," said Carrie, 54. "I went in blind. I didn't know where he was. I thought I could do some good."
Carrie said his wife wrapped the boy in a blanket and talked with him until paramedics arrived.
Karen Lowman, a paramedic with the Williamsport Volunteer Ambulance Service, said her first concern was the boy's breathing. She estimated the child had been underwater for less than three minutes and had briefly lost consciousness.
But the boy's respiratory signs were good when they arrived, Lowman said.
"He was awake when we got there. But he was real cold," she said. "He improved on the way to the hospital."
Smith and Wise said young children often play unsupervised along the river at Sportsmans Paradise, a riverside development consisting of weekend and year-round homes.
"Everybody's always hollering at the kids not to play around down there without an adult," he said.