Hopes fade for lost WA fisherman

A 23-year-old fisherman has been lost off the WA coast for more than 24 hours after the dramatic rescue of his uncle and death of his friend.

Hopes are fading fast for a 23-year-old fisherman lost off the West Australian coast for more than 24 hours following the dramatic rescue of his uncle and death of his friend.

The man, his male friend, also aged 23, and his uncle set out in a 5.5-metre fishing boat from Leeman about 270km north of Perth around 11am (WST) on Thursday.

An alarm was raised when they did not return by nightfall.

Shortly after midday on Friday, the missing man's friend was recovered from the water by rescuers who tried to resuscitate him, but he was declared dead.

About half an hour earlier, a Seven News helicopter had discovered the missing man's 49-year-old uncle, floating naked on his back, and being circled by a large hammerhead shark about 20 metres away.

The dramatic rescue unfolded in a live cross to Fairfax radio in Perth, with Seven News reporter Grant Taylor describing the frustration of not being able to help the older man, although they alerted rescuers and tried to direct him to an inflatable raft about 100m away.

They also flew low in efforts to scare the shark away.

The rescued man was flown to Perth and is being treated in hospital.

Police said the search for the third man in an area north of the Beagle Islands would continue by boat overnight.

At first light on Saturday, an air search will also be undertaken while Department of Fisheries officers comb the islands on foot.

Police divers will then try to refloat the fishermen's vessel, which has sunk in waters about five metres deep.

Police said the rescued man indicated the boat had been swamped by waves and that the three had been in the water since 3.30pm on Thursday.

The Seven News reporter later on Friday described on Fairfax radio the relief of seeing the rescue vessel retrieve the 49-year-old man, who hadn't noticed it approaching behind him and was instead imploring the TV chopper crew to help.

"He kept looking at us and kept putting his hands up in the air and you could see him mouthing 'help me, help me'," Taylor said.

"My camo (cameraman), Dave Cooper, and the pilot, Nick Scott, are both pointing out the window, saying 'look behind you, look behind you' as this (rescue) boat was coming in.

"It wasn't until the very last second that he finally swung around and saw the boat there - he was safe.

"No one's given up hope yet that the third man could actually be found alive."