It struck the water after missing the runway on the tiny island of Weno.
There were 35 passengers and 12 crew on the Air Niugini plane.
Some tried to swim ashore while others climbed on to the jet’s wings.
One passenger, US journalist Bill Jaynes, said: “I was really impressed with the locals who immediately started coming out in boats. You would have thought they’d have been afraid to approach a plane that had just crashed.
“They were awesome and I was really impressed with their whole response.”
Mr Jaynes spoke of his horror at seeing the aircraft flooding, leaving him waist-deep in water.
He added: “I called my wife and she cried. Fortunately my injury is just a head injury – there were some pretty severe ones but no deaths.”
Witness Matthew Colson said some were treated for broken legs and at least one had a broken arm.
It is understood eight remain in hospital, with one person on a ventilator.
Mr Colson said people had gathered at a market near the airport in the morning.
He said as soon as the plane hit “they just jumped into their boats and started helping”.
Air Niugini, the national airline of Papua New Guinea, said: “We thank everyone for the assistance provided.”