The officer in charge of Rottnest Island police station has revealed the heroic efforts of friends who tried to save a 38-year-old man killed by a shark on Saturday morning.

The man, who has not yet been named, was attacked at Horseshoe Reef near Rottnest Island, about 31 ​kilometres off Perth.

Sergeant Michael Wear told the Nine Network that after the horrific incident, the victim’s friends “retrieved his body from the water, gave him CPR on the way back in and came straight into the Geordie Bay jetty”.

Read said the man was on the surface of the water, spearfishing 20 metres from his boat and about a kilometre offshore, when the shark emerged.

“The injuries are quite horrific, and with respect to the family, we won’t go any further today,” he said.

A police boat at the scene. Photo: Nine Network

An RAC rescue helicopter was sent to the scene, but the injured man was unable to be revived by paramedics.

“Sadly, the man was unable to be revived,” a police spokeswoman said.

It is Australia’s second fatal shark attack this year after 12-year-old Nico Antic was killed in January while in Sydney Harbour.

A five-metre white shark was spotted 80 metres offshore about the time of the attack, according to Surf Life Saving WA.

Television news footage showed paramedics and police treating the wounded man on the jetty.

It also showed a Water Police boat tethered to a smaller boat equipped with spearfishing gear.

The Department of Primary Industries and Regional Development urged people to take extra caution in the Geordie Bay area.

Rottnest Island is a popular tourist destination 19 kilometres off the coast of Fremantle.

Police will prepare a report for the coroner.

-with AAP