Experts are baffled as to why the manager of a coal mine where four men died flouted strict health and safety regulations, a court has heard.
Malcolm Fyfield was one of seven people working inside the Gleision drift mine, near Pontardawe, South Wales, when a shaft flooded in 2011.
The father-of-two survived after crawling out through sludge and dirt.
However, Charles Breslin, 62, Philip Hill, 44, Garry Jenkins, 39, and 50-year-old David Powell all died.
Fyfield denies four counts of gross negligence manslaughter.
The pit's former owners, MNS Mining Ltd, has pleaded not guilty to four counts of corporate manslaughter by failing to ensure a safe system of work was in place.
Fyfield's trial at Swansea Crown Court has heard that up to 650,000 gallons of water gushed out of a closed-off section known as "the Old Central Workings" of the mine following the use of explosives.
Prosecutor Gregg Taylor told a jury that Fyfield should have known about the existence of the underground water.
Mr Taylor said: "Malcolm Fyfield intended to breach the Old Central Workings.
"He must have thought he could breach the workings without causing any danger to anyone.
"Malcolm Fyfield had been warned by many people about the existence of water in the old existing workings.
"Malcolm Fyfield decided to go his own way.
"It was his responsibility to follow the regulations and mine practices.
"Even if he did not believe there was any danger of an inrush it was still his duty to give his reasons to the mine's inspector.
"Malcolm Fyfield did not inform any authority about his deviation into the cautionary zone.
"Experts are at a loss to why Malcolm Fyfield did not comply with the regulations.
"His actions are harder to understand when you consider he has owned and managed coal mines previously."
In particular, the Crown highlighted two sections of the Health and Safety Executive's code of practice on preventing flooding in coal mines.
Mr Taylor said Regulation 3 stated it was the "duty of the manager" to ensure "water or material that flows" did not rush into a mine.
He added that Regulation 6 said a working mine in potentially hazardous areas should be at least "37 metres of any disused workings".
The prosecution also pointed to a hand-sketched map of the area the men were exploring on that day, September 15 2011.
It showed an area being considered to extract coal from - with the words "water" written twice on it.
It is the Crown's case that this drawing was done by Fyfield - and therefore he should have known where was safe to dig for coal.
The jury was told coal managers have to pass a precaution of inrush (PAI) scheme before any work can be carried out near areas where underground water is present.
Mr Taylor added that Fyfield had "successful" PIA applications made in the past at other coal mines - in 2005 and 1992.
He said: "Malcolm Fyfield had no problem reading mine plans and had a sound working knowledge of the regulations."
The court heard how Fyfield later tried to explain to police his reasoning for taking the mining work towards the Old Central Workings - a decision the prosecution say was "flawed".
The Crown argue the defendant made a catastrophic error of judgement in miscalculating where he thought the water line was.
Mr Taylor said: "The mine manager is there to make the correct calculations and miners' lives depend on him doing so.
"The nature of the mining industry is that mistakes cost lives.
"He did not get the men to a proper position of safety.
"They did not have chance to get to a place of safety when the shots were fired. The water came through in a matter of seconds.
"Malcolm Fyfield (showed) a disregard for the safety of his workers. The risks he took can only be described as staggering."