Two boys drowned in the Nature's Valley lagoon along the Garden Route on Saturday, the National Sea Rescue Institute (NSRI) said.
Three boys, believed to be between the ages of eight and 10, had been kayaking in the lagoon around 14:40, when they encountered some difficulty.
"One child reached the shore to raise the alarm. On arrival at the scene, a child was located and recovered from the water," said NSRI spokesperson Craig Lambinon.
Resuscitation efforts were unsuccessful, and he died at the scene.
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"During a search the second child was located and recovered from the water, but was sadly declared deceased. A counsellor assisted the surviving child, who was then taken into the care of his parents."
Lambinon said the NSRI Nature's Valley coastwatchers were instrumental in quickly evaluating and directing response resources while assisting on the scene.
The boys' bodies were taken into the care of forensic pathology services and police opened an inquest docket.
The Bitou municipality said the boys had been locals.
Both the NSRI and Bitou Mayor Dave Swart extended their condolences to the boys' families.