Washington plane crash rescue teams face huge challenge - and this could soon become a recovery mission
It's dark, freezing cold and the wind has whipped up on the Potomac River in Washington DC.
Rescue teams are working through the night in the most challenging conditions.
The plane is split in two, both it and the helicopter lying upside down in around two metres of water.
Washington crash latest: Follow updates as rescue operation continues
The shallow depth at the crash site aids the operation but the frigid temperature counteracts that.
Even if anyone survived the impact of the collision, hypothermia would pose a huge risk within minutes.
First responders were on the scene just 10 minutes after the alarm was raised by the airport control tower.
More than 300 personnel are now involved in the operation, some on boats, others diving.
Washington's fire chief John Donnelly said: "There is wind. There are pieces of ice in the water.
"And because there is not a lot of light, you are out there searching every square inch of space."
"These are very tough conditions to dive in," he added.
He confirmed the operation is entirely centred on the water and not on any land either side of it.
Ominously, ambulance crews appear to be scaling down, suggesting this will soon be a recovery mission.
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Air traffic control audio released
It's not the first time emergency teams have faced this type of challenge in this stretch of water.
In 1982, an Air Florida flight crashed on departure from Washington, claiming the lives of 78 people.