Shawn Winrich, vising Hawaii from Madison, Wisconsin, was taking photos of Pearl Harbor when he saw a helicopter "essentially coming straight at us" at a popular tourist destination that attracts thousands of visitors daily.
He switched to video, recording as the helicopter appeared to lose altitude and get closer to the water. "I thought it would be great video, whatever it is, and all of a sudden it essentially just fell out of the sky and crash-landed in the water," he said.
He stopped filming and jumped in to help.
The heads of three adults popped up, and then a fourth surfaced. He heard people saying a fifth occupant was trapped.
The Bell 206 aircraft made a hard landing and sank near the Pearl Harbor Visitor Center yesterday morning, US Navy spokeswoman Agnes Tauyan said.
The names of the five people on board were not immediately released.
"We are told bystanders jumped in to help rescue these patients from the water," said Shayne Enright, spokeswoman for Honolulu Emergency Services Department.
One of them was Chris Gardner, a tour guide with Keawe Adventures who was with a group of tourists at the visitor center when he heard the crash.
"I took off my shirt and dove in," he said, describing how he, a Navy sailor, a federal police officer and another man took turns diving to the submerged helicopter and trying to free a passenger with a knife. "He was strapped into his seat in the back of the aircraft."
They eventually freed the teenage passenger. The helicopter crashed about 20 feet offshore, right next to the visitor center's lawn, said Winrich's daughter, Justice Winrich. She watched as it "plopped down" into the water.
"I saw it like as it was coming in, and it looked pretty normal. It didn't look like it was shaking or anything," Winrich said. "It just started like getting really close this way and started going down." She thought it was strange that the helicopter was that close to people.
As it got closer to the water, she saw some dark some coming out of the back of the helicopter, and it started shaking slightly. Winrich saw three people get out of the helicopter immediately and start swimming to shore.