A WOMAN has drowned on the NSW Central Coast despite the desperate efforts of lifesavers.

The 27-year-old Bankstown woman and her friend, a 25-year-old from Casula, were swept off rocks near Avoca Beach on Wednesday.

The two women were also spotted by a passing kayaker who began paddling back to the beach to raise the alarm, Surf Life Saving NSW said in a statement.

The kayaker passed a group of teenage lifesavers on boards and asked them to help keep the women afloat until they could be rescued.

Lifeguards on jet skis brought the patients back to the beach and performed CPR on the 27-year-old as paramedics rushed to help but she was pronounced dead at the scene.

The younger woman was taken by helicopter to Gosford Hospital, where she remains in a critical but stable condition.

Surf Life Saving duty officer for the Central Coast Stuart Harvey said the young surf lifesavers had saved a life.

"Our hearts go out to the family of the drowned woman but thankfully the second patient is alive due to the quick actions of both the young board paddlers and the lifeguards," he said.