A mother of two who went missing had developed an "obsession" with walking to recover from back surgery, an inquest heard today.
Gillian Merrick, 45, disappeared from her home in Oundle, Northamptonshire, in the early hours of January 2.
Her disappearance sparked a nationwide appeal and her body was finally found in the River Nene at Tansor, Northants, in March.
An inquest today heard the mother of two had developed an obsession with walking as part of her recovery from back surgery last year, and had regularly undergone long walks in the local area.
An inquest at Kettering Magistrates Court heard Mrs Merrick had undergone back surgery for a slipped disc in November last year.
Since the operation, the 45-year-old had been keen to return to fitness, and had started walking regularly as well as completing physiotherapy.
She had insisted on walks, even when on a cruise to Amsterdam - walking on laps round the deck every day, no matter the weather - the inquest heard.
Her husband Nick Merrick, 50, told the court on New Year's Day they had spent the day together with their two teenage children Tom and Charlotte.
He said Mrs Merrick had not managed to complete her usual two walks - a distance of over five miles.
He said she was frustrated she had not done the distance she felt necessary to help her recovery, and that evening had tried to do extra physiotherapy to make up for it.
He said: "She was concerned about her lack of walking that day because she did see it as a direct link to her recovery.
"She was very aware that she had not done the walking she wanted to do and would usually do so she compensated for that by doing more physio exercises in the evening.
"Her rationale was that if she didn't do the walks she would set herself back weeks. It was an irrational obsession really."
The inquest heard the couple occasionally slept in different beds, to allow both to have a better night sleep, and that night Mr Merrick went to bed in a guest bed downstairs.
He woke his wife in the night as he collected a phone charger from their bedroom and they told each other they loved each other, he said.
Mr Merrick went back to bed and at some point heard a noise. He did not know what it was, but later thought it might have been the front door, he said today.
The next day he realised his wife had gone, and after searching in the local area for her, called the police.
Mrs Merrick's body was finally found on March 13 at Bluebell Lakes by Environment Agency workers who were removing a tree from a weir.
The inquest heard she was found wearing a coat zipped up over her face, as well as a scarf and gloves.
Home Office pathologist Guy Rutty said there were no external or internal marks to suggest a cause of death.
He said there was a level of alcohol in her body but that was likely to have been caused by changes since death.
Tests also found fluid in her chest cavity, and bleeding in her ears, which could be caused by drowning. But Mr Rutty told the inquest he could not confirm this.
The cause of death was given as unascertained, he said.
Today Mrs Merrick's distraught husband, who broke down as he took the oath for evidence, said: "I believe what happened is a terrible accident based on what amounts to a fatal decision to make up for walks that Gillian believed amounted to her recovery."
A statement from Mr Merrick read to the court said the family had been left "devastated" by her death.
It said: "She was everything to the family and was a major part of it.
"She was the glue that holds us together. I have to try to provide the love and support that Gillian did but it just will not be the same for any of us."
The inquest heard Mrs Merrick had been frustrated and "down" about her rate of recovery, but not to a level to cause her to seek medical help.
A statement from her mother-in-law Jean Merrick described how Mrs Merrick, who married her son in 1988, insisted on walking during their cruise in Amsterdam.
She said: "She said sometimes she really got so fed up not being able to do the things she really wanted."
Her statement said she had been making plans for 2009, including a trip to Portugal and plans for her husband's 50th birthday.
She said: "2009 was to have been a special year for the family.
"These would have been such family affairs and Gillian would have enjoyed so much being part of the festivities.
"Gillian's family were everything in the world to her. She loved Nick and the children to the exclusion of everything else and all she wanted was to get back to her former fitness and activities.
"To that end she felt she had to walk and walk whatever the weather and no matter the time."
Recording a verdict of accidental death, Northamptonshire coroner Anne Pember said she did not think there was anything suspicious about Mrs Merrick's death
She said: "Clearly she felt she had not walked sufficiently and in the early hours of January 2 got up to go for a walk. Sadly, her body was discovered some weeks later on March 3."