Scott MacLean, 12, and Isla Sim, 13, got into difficulty while swimming at Fraserburgh beach on Wednesday.
The youngsters ended up around 250 metres off the shoreline in an area known to have strong currents and were being dragged under the water.
Tragedy was averted, however, when the pair were plucked from the sea by an RNLI lifeboat crew who had raced to the scene.
Crewman John Chalmers, 37, risked his life when he jumped into the water to reach Scott, who was being battered by strong waves.
It was only the second time the tyre fitter had been called out on a rescue since joining the RNLI in January.
Speaking at the lifeboat station in Fraserburgh yesterday, he said: “The boat left the harbour and we got to the beach. We came alongside the female casualty and we got her on board. I was at the front of the boat looking for the younger boy. Every wave that was coming over was hitting him and we decided it was time to put someone in the water.
“I just jumped off the front of the boat and into the water and got to the casualty. The crew threw a heaving line in and I grabbed it and got pulled into the boat.”
The crew headed back into the harbour as soon as they got the boy on board and wrapped him in a blanket.
Crewman Chalmers said: “He had swallowed a lot of water – it was touch and go. If we didn’t get to him when we did it would have been a different scenario.”
Scott and Isla were taken to Royal Aberdeen Children’s Hospital where they were kept in overnight.
Fraserburgh Academy pupil Isla said she and Scott did not realise they were so far out. She said: “We didn’t really notice that we couldn’t go back until we couldn’t touch the ground. We were in there for longer than 20 minutes. It was really cold.”
Isla was drifting in and out of consciousness as she was rescued and said she could not remember much because she was exhausted.
Her mother Elaine Smith arrived at the scene and said she panicked as she ran along the beach to make sure that her daughter was safe.
Scott was making a recovery yesterday. He said: “The waves ended up splitting me up from Isla and I got scared after that as I thought Isla was under the water.
“I thought I was going to die. I stayed afloat and tried to stay calm. I can’t really remember the rescue.”
Aberdeen coastguard watch manager Kevin Brown said: “The children we recovered would not have lasted much longer. The lifeboat crew rescued them just in time.
“It is critical to always check the tidal conditions when swimming in the sea.
“The weather on scene was fine, but the hidden danger of the strong currents is something the public should be aware of.”