A lifeguard spotted Mary Stanforth face down in the water at around 12.15pm on August 13 last year and pulled her to shore with help from members of the public.
They performed cardiopulmonary resuscitation (CPR) on the beach for around 20 minutes and paramedics continued after they arrived on the scene. But the 64-year-old from Norwich was pronounced dead at 1.10pm, an inquest held in Northallerton heard on Friday.
A post mortem examination found she had been suffering with a number of health issues before her death, including schizophrenia, obesity, chronic kidney disease, and cardiomegaly.
The inquest heard that people with cardiomyopathy, which is where the walls of the heart become stretched, thickened or stiff, are at an increased risk of heart failure.
The cause of death was found to be immersion in water, obesity and cardiomyopathy.
Dr Joseph Kemp, a GP in Norwich, said she had been prescribed medication for schizophrenia and a review conducted in December 2020 found her mental health was stable.
Detective Sergeant Ellie Stephens told the inquest it was a "bright, warm day with a calm and clear sea".
She added: "I did not consider the death to be suspicious. There was no indication of third party involvement or that she had any intention to take her own life."
Coroner Oliver Longstaff said: "On entering the water, which she had done the previous day on holiday, Mrs Stanforth suffered some cardiac event which caused her demise.
"This is not a case where someone has entered the water, got into trouble and drowned. That is reflected in the post mortem evidence.
"It's also reflected in the evidence of the paramedics who told the attending police officers that the defibrillator had detected signs of a cardiac event."
He concluded that her death was an accident.