As darkness fell on Dolls Point and the police cars began to peel away, a distressed Sydney family knelt together to pray for a little boy.

An extensive water and aerial search for the child, who disappeared in the Georges River, was scaled back about sunset on Sunday and was set to resume at first light.

The father of the missing five-year-old broke down as he was led to the edge of the sand at Sandringham by police officers.

“Please, just leave me alone,” the man yelled, wailing and cradling his head in his arms as police and family members tried to comfort him.

A woman believed to be the boy’s mother was led away in tears before relatives gathered beside the St George 16ft Sailing Club to pray.

A family friend told AAP the boy had been playing in the water with his older brother when he disappeared under the waves about 3.45pm (AEDT).

Other witnesses said the boys had waded into the water outside a netted-off swimming area when the youngest was swept away by a strong current.

The family is well known among Bankstown’s Lebanese community, and large crowds remained at a section of Dolls Point, cordoned off by police until late on Sunday night.

It should have been a day of fun at the popular picnic spot at the junction between Botany Bay and the Georges River.

Families had gathered on the sand as temperatures nudged 30 degrees on the first weekend of NSW school holidays.

But dog-walker Col, 77, who did not want his surname published, said tragedy had struck this picturesque stretch of coastline before.

“If you’re not a strong swimmer it’s easy to get sucked into the whirlpools out there,” he told AAP.

Six years ago, two fiancees were left grieving after the men they were due to marry both drowned at the same spot.

The men aged 19 and 25 died in January 2007, shortly after coming to Australia from Lebanon to marry two sisters here.

It was believed the younger man had got into trouble and the other jumped in off the wharf to help.

Locals have told AAP that sand banks can create the illusion that waters off Dolls Point are shallow, but there is a deep river channel with a strong current.

The search effort involving local police, water police, PolAir, the State Emergency Service (SES) and the Westpac Life Saver helicopter ran for four hours but was visibly scaled back about 7.30pm, and police divers left the water.

An SES team also combed a stretch of beach beyond the taped-off area for signs of the boy.

It’s believed water police and PolAir will remain active overnight before a full-scale operation resumes on Monday morning.

Police say the child was last seen wearing a blue singlet and blue shorts and have urged anyone with information to come forward.