Colour Sgt Martyn Horton, L/Cpl David Ramsden, Pte Douglas Halliday and Pte Alex Isaac all died after the crash in Helmand on 23 June, 2010.
The collision forced their Ridgeback vehicle onto two wheels, before rolling into the canal, the court heard.
The inquest is due to take five days.
The hearing, at Salisbury Coroner's Court, resumed on Monday after being part heard in November,
The servicemen were members of a police advisory team, travelling as part of a two-vehicle convoy, at the time of the crash.
The vehicle, driven by L/Cpl Ramsden, collided with an Afghan National Police car by the Nahr-e Bughra canal.
The inquest heard how the crash happened as the vehicle was travelling to a police checkpoint, at the request of the Afghan National Police.
The request followed several explosions in the area.
Dr John Searle, a consultant in accident reconstruction, said: ""It was a glancing impact, an impact where the vehicle carries on and is not stopped by the impact."
He said visibility in the vehicle would have been similar to a car driving in normal night-time conditions.
Pte Michael Peers, who managed to escape from the submerged Ridgeback, said the occupants were wearing seatbelts and opened the back hatch near the water, as was recommended.
"I heard a loud bang which was like an explosion, I do not know where it came from or where it impacted, if it did impact," he said.
Colour Sergeant Horton, 34, was from Runcorn in Cheshire, L/Cpl Ramsden, 26, was from Leeds and Pte Halliday, 20, was from Wallasey in Merseyside.
Pte Isaac, 20, was from the Wirral.
All four soldiers were from the 1st Battalion The Mercian Regiment (Cheshire).

He also cancelled an investigation into claims of abuse of power revealed by covert recordings, saying he wanted to "put an end to the agony" ahead of early elections in June.
But his move was condemned both by the opposition and by EU officials.
Macedonia has been in turmoil since the recordings were released in 2015.
In a televised address on Tuesday, President Ivanov said he acted to "defend national interests".
"I've decided to put an end to the agony and, metaphorically speaking, to cut a knot,'' he said, without referring to any politicians by name.
Opposition leader Zoran Zaev said the move was illegal, urging protesters to gather in the capital Skopje. A crowd of several hundred people later gathered outside the prosecutor's office.
Meanwhile, EU Enlargement Commissioner Johannes Hahn said: "Today's actions of President Ivanov are not in line with my understanding of rule of law."
Mr Hahn added that the move put Macedonia's EU membership ambitions at risk.
The crisis was sparked by covert recordings which appear to show ministers plotting vote-rigging and the cover-up of a murder.
Mr Zaev has been releasing a steady stream of recordings since February 2015, accusing the government of wiretapping 20,000 people, including politicians, journalists and religious leaders.
He says that scores of leaked recordings reveal corruption at the highest levels of government, including the mismanagement of funds, dubious criminal prosecutions of opponents and even cover-ups of killings.
The government denies the accusations, and in return has accused Mr Zaev of trying to "destabilise" the Balkan nation.
He rejects the claim.

Gwen Thomson, 51, from Torry, died after the accident on Market Street on Wednesday morning.
Insp Jon Barron said: "Our thoughts are very much with Gwen's family, friends and work colleagues at this very sad time."
The 60-year-old male lorry driver was uninjured. Police Scotland thanked those who helped at the scene.
Insp Barron added: "We have spoken to a number of witnesses to the incident already.  However, I would urge anyone who hasn't yet been in contact with us to do so in order to help piece together exactly what happened."
An inquest into the deaths of four servicemen in Afghanistan has been told the armoured vehicle they were in rolled into a canal after colliding with an Afghan National Police car.
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Macedonian President Gjorge Ivanov has issued a pardon to all politicians embroiled in a big corruption scandal that sparked a major political crisis.
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