In the ensuing panic, the elder boy fell into the water and a man in his early 30s - thought to be their father - drowned after jumping in to try to save them.

A bystander leapt into the rough waters in a rescue attempt. He was later taken to hospital in a critical condition.

Emergency workers were called to Tathra wharf around 8.10pm.

It is understood the dead man was fishing with the two children on the wharf.

The editor of the Bega District News, Steve Strevens, arrived on the scene a short time later.

"The older child may have toppled [the pram] over, it ended up in the water and the father jumped in to help," he said. "A tourist also fishing at the other end of the wharf heard the splash and jumped in to help."

After another tourist, a woman in her 50s, called triple-0, local emergency crews assembled at the nearby Tathra Surf Life Saving Club to get to the victims.

A crew from the surf club set out in an inflatable rescue boat, while two surf lifesavers jumped into the water from the wharf despite the hazardous conditions.

After they pulled the bodies from the ocean, surf club members and ambulance crew from nearby Bega and Bermagui worked to resuscitate the four people well into the night.

"They were there for a substantial amount of time," Mr Strevens said. "They were worked on extensively by the paramedics and then transferred to the hospital. The ambulances would have left at about 9.45pm."

An ambulance spokesman said the "two children were in cardiac arrest and resuscitation continued all the way to Bega Hospital".

But late last night police issued a statement confirming that the man and the two children had died.

"Emergency services workers plucked all four from the water unconscious," police said. "The man was unable to be resuscitated and was pronounced dead at the scene. The two children were taken by ambulance to hospital in critical condition but died shortly after."

"The second man was revived by paramedics despite spending a lengthy period of time in the water."

Although the incident is not being treated as suspicious, police are calling for any witnesses to contact Batemans Bay Police Station or Crime Stoppers on 1800 333 000, as they prepare a report to the Coroner.