An elderly woman drowned after the car she was in rolled off a slipway while it was waiting for a ferry and disappeared under 30ft-deep water.
It is believed the woman was a passenger in a car waiting to board the King Harry Ferry, to cross the river Fal at the Roseland Peninsula, near Truro in Cornwall, when the accident occurred yesterday.
Reports suggested CCTV footage which captured the incident showed an elderly man, said to be in his 70s, step out of the vehicle to look at the ferry before the car suddenly rolled past him down the Philleigh slipway on the Roseland side and into the water at about 4pm.
The car ferry was across the water at the Feock side of the river, opposite the slipway, which is in a remote area surrounded by woodland.
A Devon and Cornwall Police spokesman said it is believed that other vehicles were present at the time, as well as passengers waiting to board the ferry.
It was reported at the scene that staff from the ferry company raised the alarm after they heard a big splash and saw a car sink quickly.
A huge rescue effort, involving more than 50 emergency service personnel lining both shores and on the ferry, then ensued to recover the vehicle which had sunk to the bottom of the river.
A Maritime and Coastguard Agency (MCA) spokesman confirmed that an in-shore and all-weather RNLI Lifeboat from Falmouth, containing ten rescue personnel, responded to the incident.
A rescue helicopter from RNAS Culdrose in Helston was also called, along with police and fire service vehicles, as well as a team of specialist divers from Plymouth who worked aboard a tug operated by the Marine and Towage Services in Falmouth, to recover the vehicle.
A recreational diver, who was nearby searching for cockles, is also believed to have assisted in an attempted rescue.
The ferry was moved to the middle of river where the car was winched from the water by the fire service.
It took about two hours for the burgundy car, thought to be a Toyota, to be pulled from the water, at which point it was swiftly covered by a green tarpaulin.
Medical personnel attempted CPR at the scene, before the female passenger was taken to hospital.
However, a Devon and Cornwall Police spokesman confirmed that the woman had died at the scene. He said: "The woman was in a car waiting to board the ferry and then the driver got out and the vehicle went in to the water."
The MCA spokesman confirmed the driver of the vehicle was "okay".
She said: "We can confirm that a female occupant of the vehicle was recovered from the water and was taken to hospital.
"She was in the water for sometime after the incident which started at around 4pm."
The King Harry Ferry, which has been operating since 1888, connects St Mawes and the Roseland Peninsula with Feock, Truro and Falmouth.
The service, operating all year, carries 300,000 cars every year, from Feock to Philleigh.
A statement on the Fal River website said a normal service was expected to resume this morning.
It said: "Our thoughts are with the friends and family of everyone involved in today's tragedy."
Local mussel diver Matt Vernon, who was diving without oxygen, tried to rescue the woman and dived down several times in a bid to save her.
Mr Vernon said: "It was really murky down there, the river is very deep, around 80ft, the car was down at around 25ft."
He said it was impossible to smash a window and said he tried to attach a grappling hook to the car but it was not strong enough to take the weight.