Grave fears for missing Gold Coast diver Didrik Hurum as friends join search

Police say it is "very unlikely" a Norwegian diver who went missing off the coast of Brisbane yesterday is still alive.

The man, identified as Didrik Hurum, was spearfishing at 20 to 30 metres underwater just off Point Lookout on North Stradbroke Island where he failed to resurface.

Local boat crews spent 30 minutes looking for the 25-year-old experienced free diver before they raised the alarm with authorities, sparking a massive air and sea search.

READ MORE: Recovery efforts continue after fatal Queensland plane crash

Water police and Coast Guard crews were today redeployed to the surrounding area including Amity Point and the nearby Peel Island.

Friends also joined in the search despite rough conditions.

"Very challenging for our police divers ... a very small target in a very large ocean,"  Brisbane Water Police Acting Senior Sergeant Mitch Gray said.

"It's very unlikely that young Didrik is alive … but we're not giving up." 

Sgt Gray said Mr Hurum may have suffered a "shallow water blackout" which causes a loss of consciousness.

"One of the risks with freediving is shallow water blackout. It is one of the highest risk activities you can do underwater," Sgt Gray said.

Friends told 9News Mr Hurum had suffered a blackout a few hours before he disappeared but thought he had recovered enough to re-enter the water.

Mr Hurum moved to the Gold Coast just over two years ago and had been living in Burleigh Heads while studying marine biology.

The search and rescue operation is the fourth of its kind to take place on the Brisbane coast in the past three months, following the disappearances of boatie Trent Riley and surf skier Jordan Kelly and the death of Meen Meen Chiu.