Dr Ruth Fletcher, 60, from Stocksfield, an experienced diver, was one of a group which undertook a dive from a boat at around midday on 17 July.
According to the Maritime and Coastguard Agency, Dr Fletcher lost consciousness “whilst surfacing”.
She was recovered aboard the boat, which put out a call to Humber Coastguard.
Advised over the radio by the Institute of Naval Medicine, the boat headed toward shore for a transfer by ambulance to A&E at Wansbeck Hospital in Ashington.
The SAR helicopter from RAF Boulmer was airborne and nearby. After overhearing communications, its crew was able to divert and airlift Dr Fletcher direct from the boat to Wansbeck.
Had she required recompression treatment, a further airlift to Hull would have been required. However, Wansbeck Hospital staff confirmed that Dr Fletcher had not survived.
According to the local Evening Chronicle, Dr Fletcher enjoyed canoeing as well as diving and had always been a highly able sportswoman.
She was a nationally successful long-distance runner over many years and in 1997, aged 46, became the World Veteran Masters champion at the World Quadrathlon Championships in Ibiza.