The NTSB said the aircraft had been flying about 2,000 feet (609 meters) over NY on a scheduled 30-minute flight when the pilot sent out a mayday call saying his engine had failed.
NY officials said the charter helicopter was hired for a photo shoot.
At least two of the passengers were dead by the time rescue divers arrived, police and fire department officials said.
Fire Commissioner Daniel Nigro said: "It took a while for the divers to get these people out". Vance was the sole survivor.
A spokesperson for Liberty Helicopters was not immediately available for comment. Providing sightseeing trips since 1990, the company advertises "unparalleled safety records".
"There are a whole lot of questions about this crash", he said.
"One of the most hard parts of the rescue were that five people were tightly harnessed", Nigro said.
A federal official, who wished to remain anonymous, told news agency AP the pilot, Richard Vance, 33, believed a luggage item belonging to one of the passengers had hit an emergency fuel shutoff switch.
Ms Dinh-Zarr also said it was legal for doors to be open on this model of helicopter, and safety floats did inflate on the helicopter as it made contact with the water. "It's really horrifying and I hope that something come from this", Adams said adding that while the tragedy was a wakeup call he would continue seeking these kinds of aviation experiences. A passenger on board a sister flight operated by FlyNyon Sunday night said the company showed a safety video but didn't physically demonstrate how to escape the harnesses.
"We are giving urgent attention to the use of harnesses specifically for aerial photography flights". "All he has to do is pull up one lever and the seatbelt comes apart, and he's practiced getting in and out of the aircraft hundreds and hundreds of times and knows exactly how to do that". He said the pilot had initially thought that the passengers survived.
The harnesses, which are different than traditional aircraft seat belts, are created to allow people to safely photograph from a helicopter with the doors open. On their back, between their shoulder blades, was a metal ring attached to a carabiner and tethered to the floor.
Cuenca del Plata University in Argentina said she studied art, design and communications. "You can't expect people who are untrained to watch a video, and then, without any real hands-on drill, expect them to react in survivability mode".
A helicopter is hoisted by crane from the East River onto a barge, Monday in NY. In August 2009, nine people were killed after a helicopter and a small, private plane crashed into each other over the Hudson River.