A scuba diver is lucky to be alive after members of the public performed CPR on him after he was pulled from the water on the NSW south coast.

The man, aged in his 60s, was diving at Kiama when he got into difficulty about 8.45am (AEDT) on Wednesday.

Another diver pulled him from the water unconscious and on to an isolated area of the shoreline where he was revived.

A spokesman for the Ambulance Service of NSW said paramedics arrived within seven minutes.

"He was lucky to have someone near him that knew CPR," the spokesman told AAP.

A rescue helicopter winched the diver from the coastline before he was transported to Wollongong Hospital in a critical condition.