Emergency services have concluded day three of the search which included divers and air patrols of the waters and beaches south of Port Macquarie to Bonny Hills and North Haven.

The family of the 11-year-old from the ACT wait for any news their boy has been found.

The conditions at Lighthouse Beach and along the Hastings coastline on Wednesday, December 6 were treacherous.

Wading in the waves with his older brother, it is believed the boy lost his feet in an undertow and got caught in a rip.

Despite the best efforts of his 17-year-old brother, who attempted to save him, the boy disappeared into the waves and has not been seen since.

An emergency services alert was issued just after 1.30pm with Marine Rescue Port Macquarie, lifeguards, emergency services crews and the Westpac Rescue Helicopter responding. Bystanders on the beach assisted the family until help arrived.

Around 20 surf lifesavers and lifeguards are also involved in the search effort which involves three local surf life-saving clubs.

Among those were Greg and Kim Thomas of Port Macquarie who said the incident is nothing less than a tragedy felt by the entire community.

“The young fellow was in a lot of distress. We helped him with the ambos - he was in shock,” Mr Thomas said.

The young boy was waist-deep in the water when he was dragged out and his older brother tried to rescue him, NSW Police Inspector Peter Neville said. His frantic mother watched on.

"The elder boy tried to assist the 11-year-old but was unable to pull him from the surf," Inspector Neville said.

The brother was treated for exhaustion by ambulance paramedics.

NSW Ambulance Acting Superintendent David Horseman said the family is being supported as the search continues.

“The NSW Ambulance and Westpac Helicopter plus Marine Rescue are doing their very best to locate the missing child,” he said.

Divers, IRBs and the Westpac Rescue Helicopter along with surf drones are searching from the air, land and water as far south to Bonny Hills.

Surf Life Saving NSW issued a statement saying conditions along the coast have been incredibly challenging.

“This is an extremely difficult operation and our thoughts are with everyone involved,” said SLSNSW CEO Steven Pearce.

“We will continue to support the police and other agencies with whatever surf lifesaving assets are required.

“In the meantime we urge people to take care along the coast. We are imploring people to swim only at patrolled locations, in between the red and yellow flags this summer,” he said.