Mrs Reed was preparing for a Maldives diving holiday
Janet Reed, 34, was taking diving lessons as a treat for herself and her husband to prepare for a holiday in the Maldives.
She enrolled herself and husband Andrew on a five-week course run by Hydroactive Outdoor Pursuits of Hertfordshire in March 2001.
The mother had reached the programme's final dive at the Stoney Cove National Diving Centre, which is located at a Leicestershire quarry, when the accident happened on 18 March.
Murky water
She is thought to have panicked when she had problems clearing her ears under the increasing water pressure.
Mrs Reed, of Potters Bar, Middlesex, struggled free from a more experienced diver, losing her air supply and isolating herself in the murky water.
She was eventually rescued but had been under the water without air for nearly 15 minutes and never regained consciousness.
She was rushed to hospital but died five days later when life support systems were switched off, the Leicester inquest heard.
Misadventure
Her husband Andrew, who had been swimming with the main group of divers nearby, was unaware of the accident until he surfaced minutes later.
Representatives of Hydroactive Outdoor Pursuits were questioned about their safety procedures throughout the three-day hearing.
But Leicester coroner Martin Symington told the jury there were no grounds for a verdict of death by neglect or lack of care.
It took the four-man, three-woman jury just 30 minutes to return a verdict of death by misadventure.