An off-duty police officer has drowned while trying to save his teenage son from a rip on a beach on the NSW Far South Coast.

The man, 45, died during the brave rescue of his 14-year-old son near Narooma on New Year's Day.

Surf Life Saving NSW said the man was also caught in a rip at Bogola Beach, which is unpatrolled.

READ MORE: Charity plea as junk litters streets outside shops

Local lifesavers rushed to the beach in an inflatable rescue boat at 1.30pm but despite giving CPR, the man couldn't be saved and he died at the scene.

NSW Police Acting Inspector Paul Hoyer from Nowra Police Station said the officer worked in the North West Metropolitan Region, which covers a large part of Sydney's north and west.

He's understood to be based at Springwood in the Blue Mountains.

The off-duty officer was on a family holiday when he rushed to the rescue of his son, who was caught in a "substantial" rip in the ocean.

"He was able to push his son out of the rip, he was then taken further out to sea in the rip," Hoyer said.

"This is a tragedy which will cut through to the family, his friends and workmates.

"It's devastating."

READ MORE: Where Aussies want to go in 2023 – and how to get the best deal

Hoyer praised the officer for his actions.

"As a father, parent and police officer, he was obviously doing what he should be doing," he said.

Hoyer urged people to swim between the flags at patrolled beaches.

Police said officers from South Coast Police District will prepare a report for the coroner.

NSW Surf Life Saving said large crowds flocked to beaches on New Year's Day.

The drowning is just the latest over the festive period, with multiple people losing their lives in water-related incidents across the nation.