An abalone diver has been taken by sharks while diving south of Perforated Island near Coffin Bay.
Police say the diver was returning to the surface on Thursday afternoon when two sharks, believed to be Great Whites, attacked him.
The skipper on the boat witnessed the tragedy and has since returned to shore.
Port Lincoln detectives are investigating the death.
A spokeswoman for SA Ambulance Service said paramedics were on the jetty when the boat returned and the skipper was treated for shock.
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She said the man was the only person on the boat when it arrived back at Port Lincoln.
"I don't know exactly what happened but he came back alone," she told AAP.
