A jury has heard how miners working at a coal mine where four men died following flooding heard an explosion "like a jet engine" moments before the sudden whooshing sound of water.
Pit boss Malcolm Fyfield was one of seven people working inside the Gleision drift mine, near Pontardawe, South Wales, when a shaft flooded in 2011.
He survived after crawling out through sludge and dirt.
As he was being treated by paramedics, Swansea Crown Court heard he told paramedics: "They've gone. There is no hope for the others."
Following hours of searches, the bodies of Charles Breslin, 62, Philip Hill, 44, Garry Jenkins, 39, and David Powell, 50, were discovered.
Father-of-two Mr Fyfield has pleaded not guilty to four counts of manslaughter.
MNS Mining Ltd, which ran the mine at the time, denies four charges of corporate manslaughter by failing to ensure a safe system of work was in place.
Prosecutor Gregg Taylor said coal was extracted from the 100-year-old drift mine using explosives.
Conditions in the mine were said to be cramped, with the ceiling height at just 77cm, almost 20cm lower than a standard kitchen work top.
Mr Taylor said: "Men worked this 2ft space by crawling on their hands and knees.
"It's not modern ... with machines, tracks and trains. This is a very historical practice."
Mr Taylor said that at around 9am on September 15, a mine worker called David Wyatt told colleagues he was going to "fire the shots" - to blast the coal from the seam.
Mr Taylor said: "They heard an explosion that sounded like a jet engine and their reaction was to shout 'run'."
The jury was told the "deafening sound" of rushing water followed.
Mr Wyatt and a colleague called Nigel Evans managed to flee up the main shaft with the water close behind.
A frantic 999 call was then made by the late Mr Powell's son, who also worked at the mine.
After being discharged from hospital on September 27, Mr Fyfield told police what he encountered while he was trapped inside the mine.
The jury was told that the defendant found David Powell and tried to give him mouth-to-mouth resuscitation in a flooded stall where there was only 4in (10cm) of headroom.
Re-telling Mr Fyfield's account, prosecutor Mr Taylor said: "David Powell was showing no signs of life.
"It was not possible to get a pulse because of the debris around."
The pit boss then found Philip Hill about 16ft (5m) away, "wrapped around a timber prop".
Mr Fyfield attempted mouth-to-mouth again, but air he tried to breathe into Mr Hill's lungs came straight back out - suggesting that they were blocked with water.
With water levels rising fast, Mr Fyfield then made his exit.
Mr Taylor also gave details of the post-mortem examination reports.
He said all the men's lungs and airways were blocked with "coal-contaminated and silt" water.
Addressing the jury directly, Mr Taylor asked: "How did this happen? How did such a tragedy occur?"
He said the key to answering these questions would be photographs and maps of the drift mine.
Of the latter, he said plans of the mine had to be updated by Mr Fyfield every three months.
Mr Taylor said the defendant was described as "very experienced" in mining and had owned and run a number of collieries - such as Nant Hir in the Neath Valley.
"As a mine manager, Mr Fyfield was very well-regarded in the industry and by the Mines Inspectorate," he said.
The jury was also told that Mr Fyfield had been working as Gleision's manager 10 weeks before the disaster.
The jury was also told about the layout of the mine.
Mr Taylor said Gleision being a drift mine meant colliers walked or crawled down a gradual slope to retrieve coal.
The main shaft, serviced by a conveyor belt, was 275 metres long - with the entrance 145 metres above sea level.
Offshoots from the main shaft, or stalls, were where miners would retrieve the coal from.
Pointing to an area on a map shown to the court, Mr Taylor said the stall where the four men died was 100 metres off the main shaft.
At this point, the height above sea level was around 86 metres.
The prosecution also said that to work the drift mines, water had to be constantly pumped out.
Mr Taylor also explained to the jury that since the incident, Fyfield now suffers with "severe post traumatic stress disorder".
He has been given permission to leave the courtroom if he feels unable to listen to some of the evidence.
Fyfield, who was sat next to wife Gillian, remained in court and heard all of the proceedings on the first day of his trial.
A few feet away from him were two representatives of MNS - Maria Seage and Gerald Ward.
The court has heard the name MNS comes from Miss Seage's full name - Maria Nora Seage.
The trial is set to continue tomorrow.