Aberdeen Coastguard received an emergency call from a member of the public who saw the two girls and a boy being dragged out to sea by the current off Fraserburgh beach, opposite Tiger Hill, this afternoon.
The Fraserburgh RNLI lifeboat went to the scene where they found the children dipping below the water, cold and exhausted.
They were were brought back to shore suffering from mild hypothermia and an ambulance took them to hospital for a check. All three were "fine", the Maritime and Coastguard Agency said.
Watch Manager Kevin Brown said: "The children we recovered today 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. If you do get into difficulty, dial 999 and ask for the Coastguard."