A Highway Patrol officer entered the sea with a flotation device and swam out to two of the men, before they were rescued and taken ashore.
Emergency services tried to revive the 30-year-old from Lakemba, however he died at the scene.
The police officer and the second man, aged 42 from Wiley Park, were not injured.
About the same time, the Toll Helicopter crew had winched the third man from the sea who died a short time later.
None of the men were wearing life jackets.
The rock platform is the same location where three men died last month after they were also swept into the sea while fishing.
