The man was aboard a motor cruiser which had been approximately 27 miles south east of Eyemouth, but was now heading to Seahouses.
The diver had been diving to approximately 61 metres for about 38 minutes, and became ill when he surfaced.
The all-weather lifeboat from Seahouses was called out by Humber Coastguard at 6.41pm, while the rescue helicopter from Inverness had been tasked and was on its way.
The lifeboat crew was requested to give medical care to the diver until he could be handed over to the helicopter.
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The lifeboat crew was put aboard the motor cruiser and the diver was found to be very ill and his condition was causing some concern. He was given oxygen and carefully monitored.
On arrival of the rescue helicopter, the diver had been transferred to the lifeboat and made ready for a helicopter evacuation. He was then flown to the decompression chamber at Aberdeen for treatment. The diver was believed to be from the Glasgow area, but the RNLI has no further information as to his identity or condition.
Seahouses Lifeboat Operations Manager Ian Clayton said: “This diver was really very poorly when transferred to the helicopter. We hope he is able to make a full recovery, and he is now in the best place to do so.”