Kellie Poole, 39, died on April 25 last year after suffering a “sudden cardiac death” believed to have been triggered by the cold water during an immersion session in the River Goyt in Whaley Bridge, Derbyshire.
The session was run by Breatheolution, led by Kevin O’Neill, who also gave evidence before the inquest at Chesterfield Coroner’s Court on Tuesday.
After the court heard from an environmental health officer that the activity is not regulated, Ms Poole’s mother, Diane Service, called for more to be done.
She said: “I can’t believe that these activities are not regulated. I know it is nobody’s fault, but I just can’t believe it.
“It is a change that needs to come very soon. It is too late for Kellie, but not for someone else.”
At the end of Tuesday’s hearing, Ms Poole’s father, Frank Service, accused Mr O’Neill of “not giving it 100 per cent” to look after his customers and said he “needs to put more effort in”.
Ms Poole, from Droylsden, Tameside, Greater Manchester, was taking part in the session led by Mr O’Neill on the edge of the Peak District with two friends when she complained of a headache, before falling.
She received CPR after she was pulled from the water, which had a temperature of about 11C, but was pronounced dead at the scene.
The inquest heard that the cause of her death was given as sudden cardiac death, caused by left ventricular hypertrophy – a thickening of the walls of the lower left heart chamber – which could have been triggered by the cold water.
One of Ms Poole’s friends, Victoria Fielding, told the court that a written waiver was not signed, but Mr O’Neill verbally asked them if they had any health conditions.
Giving his evidence, Mr O’Neill said he did not have paper waiver forms at the time of Ms Poole’s death, but equally was not expecting people to bring the forms with them.
He now has paper waiver forms for those who take part in his sessions, but also called for regulation of the activity.
He said: “There is not enough regulation, I wholeheartedly agree with that.
“I have witnessed every reaction possible in the cold in the last three years and it does need regulating.”
When asked by his solicitor, Jennifer Ferrario, whether he believed anything could have been done to save Ms Poole, Mr O’Neill said: “No, I don’t think there is anything anybody could have done.”
Pauline Forrester, an environmental health officer for High Peak Borough Council, who investigated the “tragic incident”, told the court that she found “no guidance” for cold water immersion.
While Mr O’Neill has completed a first aid course and written risk assessments since the incident after advice from environmental health officers, Ms Forrester added these were also not legal requirements.
Speaking after the evidence, Peter Nieto, senior coroner for Derby and Derbyshire, said that the cold water exposure likely contributed to Ms Poole’s death “on the balance of probabilities”.
He said: “I don’t see how it would have been possible for Mr O’Neill to foresee that Kellie would get into the difficulty she did and sadly die on the riverbank.
“Quite simply, he did not know that she had a very serious cardiac condition and she did not know herself, so I don’t think it is possible to say her death could have been avoided.
The inquest, set to conclude on Wednesday, continues.%n