The body of a five-year-old boy who vanished in a Sydney river on Sunday has been pulled from the water by police in a horror 24-hours on NSW waterways.

On a day in which a man’s body was dragged from the Murray River and a fisherman was swept from rocks at Jervis Bay, the five-year-old’s body was found underwater by police divers around 10am (AEDT).

The young boy had been playing in the water with his older brother at a popular picnic spot between Botany Bay and the Georges River at Dolls Point on Sunday afternoon when he disappeared under the waves.

A massive search by local police, water police, PolAir, the State Emergency Service (SES) and the Westpac rescue helicopter failed to locate the boy on Sunday, and resumed on Monday with the aid of volunteers.

Police said the boy’s body was found several metres from the shoreline in water about 4.8 metres deep where the ocean floor dropped steeply.

There were strong currents in the area and visibility was very poor, police said.

St George Local Area Commander Superintendent Dave Donohue said the boy’s mother was “devastated” after being told the news.

“It’s very traumatic. We all have kids. It hits home,” he told reporters outside the Georges River Sailing Club.

His message to beachgoers was “play safe and be safe”.

“You need to understand the conditions you’re swimming in, and no matter you go where there’s water (have) good supervision of your children,” he said.

“It really hits home at this time of year leading into the Christmas period.”

Meanwhile, authorities on Monday also recovered the body of a man who went missing after swimming in the Murray River on Saturday.

The man, 44, from Mount Pritchard, was camping with his family when he went for a swim alone in the river near Bruce’s Bend at Yarrawonga, on the NSW-Victoria border, on Saturday afternoon.

After searching the area over the weekend the man’s body was located by an SES volunteer about 9am (AEDT) Monday.

In the third incident, a fisherman was washed off rocks at Jervis Bay in the early hours of Monday morning.

Police said the 28-year-old, from Winston Hills in Sydney, had been with friends on a rock platform at Little Beecroft Head when he was swept into the sea.

The man wasn’t wearing a lifejacket and couldn’t swim, a police spokeswoman told AAP.

The search for the man was suspended on Monday afternoon.