A man has died after he was swept into the ocean by a large wave while fishing off rocks on Sydney's south coast.


The 58-year-old man was struck by the wave and washed into the water while fishing with a friend on a rock shelf near Kendalls Beach on Friday about 7.30pm.


The fisherman's companion ran to nearby residents to raise the alarm and paramedics and police searched the area for him using a rescue helicopter and boat.


He was not wearing a life jacket and was pulled from the water about an hour after the search started.


Illawarra Ambulance District Inspector Terry Morrow said he had been swept about 200m to 250m from the shore.


“It was freezing cold conditions,” Inspector Morrow said.


The fisherman could not be revived and was pronounced dead. His companion was treated for shock at the scene.


A Surf Life Saving NSW spokeswoman said conditions at the time were particularly dangerous as waves were unpredictable. She said the location was a “black spot” for rock fishing accidents.


“It's quite rough around those rocky platforms. We did put a dangerous surf warning out earlier this week and although we dropped that there was still a long period swell at the time which is what we call it when there is a long gap between larger sets of waves,” the spokeswoman said.


“There is not much you can do when it's dark and you don't have a life jacket on. You've got little to no chance.”


A report outlining the full circumstances of the fisherman's death will be prepared by police for the Coroner.


Police have urged rock fisherman to have access to safety equipment and to constantly monitor the ocean for any deterioration in conditions.