A competitor in the Great North Swim is recovering in hospital after suffering a suspected heart attack while taking part in the event.
The event was marred by tragedy on Saturday when another man died during a race.
The latest incident took place at around 8.30am on Sunday when the man, aged about 50, suffered a heart attack and stopped breathing, the Great North Air Ambulance Service (GNAAS) said.
Emergency crews attended the scene, on Windermere, and the Air Ambulance's Pride of Cumbria helicopter was dispatched.
The victim was resuscitated by doctors before being flown to hospital in Newcastle-Upon-Tyne where he remains in a "stable" condition.
A GNAAS spokesman said: "The man had suffered a cardiac arrest, his heart was not beating and he was not breathing.
"The Pride of Cumbria helicopter responded to a call from the North West Ambulance Service and arrived at the scene. Doctors from the charity managed to resuscitate the patient and he was anaesthetised before being airlifted to the Royal Victoria Infirmary in Newcastle."
Around 10,000 people were taking part in the three-day Great North Swim which involves half-mile, one-mile and two-mile swims on Windermere in groups of up to 300 people.
Many of the swimmers are amateurs raising money for charity.
A one-minute silence was held before Sunday's races in honour of the 46-year-old local man who died while competing in a one-mile race earlier in the weeekend.