Lois Kemp was patrolling the swim zone when she noticed the two children between the red and yellow flags.
They were trying to hold onto each other to stay afloat in the water when Lois entered the water with a rescue tube.
She used it to support both children and when they were both calmer, Lois returned them safely to shore.
Luckily, neither sustained any injuries.
Lead Lifeguard Supervisor Arun Gray congratulated the brother sister duo for choosing a lifeguarded beach:
‘The children sensibly chose to swim at an RNLI lifeguarded beach between the red and yellow flags," he said.
"They followed our safety advice perfectly and as soon as they found themselves in any trouble, one of our lifeguards was around to help."
For more information on beach safety, please visit: https://rnli.org/safety/beach-safety