Wyndham is a tiny village on the Far South Coast with a population of less than 400. Today every one of those residents is likely to be mourning the loss of an innocent child on Monday.

The 10-year-old boy was digging on the remote Terrace Beach, between Pambula and Eden, with a four-year-old sibling, enjoying the first day of the school holidays, when a sand dune collapsed, trapping him.

The younger sibling ran to the boy's mother, and she alerted other beach-goers, who tried to help get the child out.

Paramedics treated him at the scene but he died at Merimbula Airport, before he could be airlifted to Canberra Hospital on Monday.

Bega Valley Mayor Bill Taylor said the little boy went to Wyndham Public School and the close-knit community would be reeling.

"In a village like that, everyone knows everyone," Cr Taylor said.

"We can only struggle to comprehend how family and friends are coping today. We can't even imagine what they are going through.

"It's every parent's nightmare that something like this might happen. A child doing something so innocent and the next minute you have a tragedy on your hands.

"We send our heartfelt sympathy to the family and friends."

Detective Superintendent Peter O'Brien described the accident as "a tragedy of immense proportions".

"They were just doing what all kids do on the beach, digging holes and mucking around," he said. 

"Something that would be happening every day on every beach in Australia. This one, unfortunately, has turned into the tragedy we are talking about."