A spokeswoman for Northumbria Police said earlier: "At 4.10pm we received a report expressing concern for a man in the sea near to Marsden Grotto.
"Police and the coastguard attended and located the man in the water.
"He was lifted from the sea by a RAF helicopter and taken to the RVI hospital with life-threatening injuries."
A spokesman for the RNLI said the man had entered the sea in a state of distress.
"Arriving at the scene the three RNLI volunteer lifeboat crewmen commenced searching for the casualty. The RAF helicopter arrived shortly afterwards and located him floating approximately 100 yards from the beach," the spokesman said.
The man was winched aboard the helicopter and taken to Newcastle's Royal Victoria Infirmary.
All other search teams were stood down and the lifeboat returned to station.
Adrian Don, spokesman for Tynemouth RNLI lifeboat, said: "The search and rescue operation for the casualty was co-ordinated throughout by Humber Maritime Rescue Coordination Centre and involved the RNLI volunteer crew working with the RAF rescue helicopter crew to effect as fast a rescue as possible to give the casualty the best chance of survival.
"All RNLI volunteer crew members are trained to a high standard of casualty care but on this occasion one of our crewmen was also a trauma doctor and he started resuscitation on the casualty before passing him into the care of the RAF winchman, who is a trained paramedic."