A sheet had been put over her and the number of people standing around made it hard to see exactly what was going on.
He was initially concerned the woman had been seriously hurt because she was lying motionless.
"They weren't even poking her leg and there was no response."
Aucklander Ian Baker was impressed by the woman's courage during her ordeal, which he said lasted about half an hour.
"She was just lying there, quiet as. She didn't seem to be in a lot of pain."
The woman, who he described as being aged in her late 30s or early 40s, was sitting up and alert when she was taken to a waiting ambulance.
But one of her lower legs was badly bruised, Baker said.
"The whole back of her calf muscle was just black."
A large crowd gathered while firefighters worked to free her, which included using a skill saw to remove a piece of wood next to the ride, but most people were asked to move away.
The ride, one of the park's most popular, was closed while park staff made repairs, including lowering the fence where the woman's leg is thought to have become trapped. The ride reopened about two hours later.
A Rainbow's End manager, who did not want to be named, would not comment as the park planned to release a statement. But that statement was not available before the Herald on Sunday deadline.