Malcolm Fyfield has suffered severe post traumatic stress disorder since surviving the flooded Gleision drift mine in September 2011.
He told Swansea Crown Court the only sign of water near the point being mined was "ponding" on the ground.
Mr Fyfield and owners MNS Mining Ltd deny manslaughter charges.
David Powell, 50, Charles Breslin, 62, Philip Hill, 44, and Garry Jenkins, 39, died when 650,000 gallons of water rushed into the area they were working in after they blasted into a flooded old section of the pit.
Mr Fyfield managed to escape and spent 12 days in hospital recovering from a broken hand and bruising and swelling as a result of a "near-drowning experience".
The former mine manager insisted he had not inspected the wrong part of the mine and said he was sure he was not mistaken because of the angle and gradient of the underground road.
The jury was told Mr Fyfield also suffers from "survivor guilt" and certain words used to describe the flooded mine trigger a feeling of being back in the pit.
Elwen Evans, QC, defending, told the court that "ponding" water found in the area before the controlled explosion was not unusual and Mr Fyfield did not think it was particularly significant.
Miss Evans reminded the jury Mr Fyfield was working alongside the men, adding: "It would have been incredibly reckless to make the breakthrough at a location he had not inspected, putting at risk the lives of four men as well as his own.
"We are dealing with someone whose reputation was as sky high as it comes.
"Year after year he did everything by the book. He knew how to do it, but this time he did not? It does not make sense."
Miss Evans asked the jury to decide the case according to the facts and to not base their verdicts on emotion.
The trial continues.

A letter from Petitions Committee chairman William Powell to the education minister said there was widespread confusion over the policy.
The committee is investigating after thousands of complaints from parents.
It comes as figures show the number of fines varies between councils.
A BBC Wales Freedom of Information request found Cardiff council issued 370 fixed penalty notices between January and May.
During the same period, 10 other councils, including Monmouthshire which has not yet introduced fines, did not issue any.
In his letter to Huw Lewis, Mr Powell said the committee was concerned many councils were incorrectly advising schools only to authorise term-time holidays in "exceptional" circumstances, with some asking head teachers not to authorise any at all.
Speaking on the issue, before the letter, Mr Powell said: "The relationship between parents and schools is absolutely crucial and I think it's potentially very damaging to have this rather aggressive approach being brought in.
"We need to have a degree more common sense."
The Welsh government has said parents do not have an "automatic right to withdraw pupils from school for a holiday and they must apply for permission in advance".
But it does give schools "discretionary power to authorise up to 10 days absence during a school year for family holidays during term time".
Two campaign groups have drawn up petitions calling for children to be allowed term-time holidays. The largest petition, with 18,000 signatures, is from a group called Let Children in Wales Have a Family Holiday During Term-Time. The other petition has been drawn up by Pembrokeshire Parents Want a Say.
Campaigner Bethany Walpole-Wroe, from Llanybydder, Carmarthenshire, said many families could not afford to go away during school holidays.
"The prices more than double usually in July and August, so they either can't afford them or they can't get time off due to various circumstances," she said.
But the Welsh government said school attendance should come first.
Education Minister Huw Lewis said: "Prolonged absence from school really does damage the attainment prospects of young people and that's why I, and I think most parents, would put learning as a priority."
Head teachers' union National Association of Head Teachers (NAHT) Cymru said while everything possible should be done to ensure children have the least amount of time out of school, it would not encourage its members to fine parents.
Campaigners will find out in the new year if the committee intends taking any action.
The manager of a mine where four workers drowned checked three times for any signs of water or danger the day before it flooded, a court has heard.
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Some parents who have been fined for taking holidays in term-time may have been dealt with unfairly and unlawfully, an assembly member has claimed.