By Steve Almasy, Julia Jones and Jason Carroll, CNN

When a charter helicopter crashed into the Hudson River on Wednesday, the captain of a nearby ferry wasted no time coming to the pilot's aid.

"We just go and we just act," Capt. Adam Sciaino said. "There's no thought process. Just your instinct. You get on the radio and, and do what you're supposed to do."

The pilot was moving his aircraft from the fueling area to the customer section of the West 30th Street Heliport, and had trouble as he reapproached the facility, NYPD Assistant Chief Stephen Hughes told reporters.

The pilot, who only suffered a hand injury, deployed the helicopter's flotation equipment, keeping the aircraft from sinking.

Sciaino, who was shuttling his last load of passengers for the day, saw the aircraft in trouble and diverted his course. He estimated he was there in 30 seconds.

He told a deckhand to get on the bow and put a rescue cradle in the water. From his position he couldn't see the man in the water as he drew near so the deckhand used finger signals to get them close for a rescue.

Then he got a glimpse of the crash.

"He's standing on the side of the helicopter holding on," Sciaino said, adding that he used his loudspeaker to give the pilot instructions. "He turned, grabbed the ladder and came up."

It was the second water rescue in a decade for Sciaino. Ten years ago, he helped rescue a man stranded under a pier in winter. He also ferried people from New York after the September 11, 2001 terror attacks.

Dock worker suffers minor injury

A dock worker who was trying to get out of the way of the helicopter was also injured after he slipped and hurt his wrist, police said.

Ashton Byrd was walking with a friend when he saw the helicopter going down, and managed to capture it on video.

The footage shows the aircraft descending toward the water with its nose down and its rotors moving. The helicopter appears to level out and as the pilot deploys floatation devices as he gets close to the water.

"It was the craziest thing I've ever seen," Byrd said.

Byrd said the helicopter appeared fine as it took off, but then the motor began to whine.

"He was just kind of spinning and then the helicopter got sideways on him and then that's when it started going down," Byrd said.

CNN affliliate WABC aired video from a different angle that shows the helicopter flying normally above the water as a ferry goes by. The rotors suddenly appear to slow slightly, and the aircraft spins twice and begins to drop with the nose pointing down. The crash occurs behind a tree line, but a piece of debris can be seen flying away.

The helicopter was a Bell 206, Federal Aviation Administration spokesman Jim Peters said.