Nine boys were walking on the ice just before 6 p.m. at the pond near Central Park South and Sixth Avenue.
A witness said he saw the group go out onto the ice, where they were taking selfies and jumping on the ice -- then they broke through the surface.
Seven fell into the water when the ice cracked and had to be rescued.
"They're together, and they said 'let's take a selfie,' and they went all down," said eyewitness Maia Ramirez.
Two Good Samaritans -- Bennett Jonas and Ethan Turnbull -- were nearby and saw them fall into the icy pond. They ran over to help when they heard screaming.
Watch as Jonas and Turnbull described the difficult rescue:
Jonas said he knew he should not have gone into the freezing water, but said they didn't have time to wait. As they pulled them out, one by one, the conditions of the teens worsened.
When he got to the last one in the back, Jonas said he was struggling to reach him -- but found his backpack, grabbed it and pulled the boy up out of the water.
"If I didn't grab him, a second later he was gone," Jonas said. "He was barely breathing."
The boys, ages 13 to 17, were taken to three hospitals, battling minor hypothermia. They were all expected to be treated and released.
Two other boys who didn't fall through, ages 13 and 14, left the scene and were later tracked down in East Harlem.
An Eyewitness News viewer snapped this photo of the scene as the rescue operation was underway:
Watch exclusive, unedited video showing first responders rush the victims into awaiting ambulances:
The big concern was the temperature of the water. Meteorologist Lee Goldberg has some perspective: