Kindergarten student Ayman Ksebe only escaped his family's eyes for a few seconds.
But it was just enough time for the five-year-old to dart across the sand and into the water where he could not swim.
As his family shared a picnic on a grass reserve overlooking a southern Sydney beach, little Ayman slipped off a sand embankment into deep water about 4pm on Sunday.
Police say his 14-year-old brother Rami ran towards him after he saw his head slip under the water a few metres off the shore of Sandringham Beach.
He grabbed hold of his little brother but he was ripped from his grip by a strong current.
"He started losing his footing at the drop-off, dropped his brother and watched him slip into the deep water," water police said.
He yelled out for help but by the time an uncle reached the water, Ayman had vanished beneath the surface in front of Georges River 16ft Sailing Club.
Police divers found his body resting on the ocean floor on Monday, only 70 metres from where he had fallen into the water.
Botany Bay Water Police walked slowly up the beach towards his family on Monday morning and told his father Azzam and mother Rouba Ksebe the body of their youngest son had been found.
Senior Sergeant Brett Prentice said it is not something he ever wanted to do again and urged parents to watch their children - no matter where they were swimming.
"It really highlights the dangers of not supervising children, especially if their children aren't taught how to swim.
"Every piece of water is dangerous if you can't swim."
He said the stretch of water where the Georges River meets Botany Bay was not a dangerous spot but that tragedy could strike anywhere in the water.
"It's going to be a warm summer and all parents should be extra vigilant when watching their children from backyard pools to swimming at the beach."
Ayman's family said they wanted the Condell Park Public School student to be remembered as a bubbly little boy with a big smile.
"Best smile, most bubbly little boy. He was adored by all. We absolutely loved him. We are all really going to miss him," his uncle said.
Rouba Ksebe clutched a much-loved stuffed animal and walked down to the water's edge with more than a dozen family members an hour after hearing the news of her son's death.
Azzam Ksebe was comforted by police as he sat in Peter Depena Reserve and was shaking as he was helped to the car park.
In the days leading up to Christmas there have been two other drowning tragedies across NSW, including the death of a Thai tourist at Maroubra and the drowning of a 44-year-old Sydney man in the Murray River.