A man has drowned at Hutchison Reef off Moreton Island near Brisbane in an apparent free diving incident, Queensland police say.

Authorities said the 19-year-old was with three friends about 7:30am when he blacked out near the surface and sunk into 30 metres of water.

He was brought to the surface but could not be revived.

Free diving is a form of diving where participants hold their breath rather than using breath apparatus.

Brisbane Water Police Sergeant Shaun Harrison said the four men had gone fishing about 4:00am.

"Four young guys had gone out for a recreational spear fishing and free diving day out north of Cape Moreton," he said.

"About 7:00am, one of them has blacked out whilst returning to the surface of the water and unfortunately sunk to the bottom out of the reach of his mates ... they weren't able to grab him."

Sergeant Harrison said the man was still wearing a weight belt.

"One remained in the boat at all times. There were three in the water," he said.

He said the man's two mates who surfaced before him turned around and saw him drifting back down to the bottom in "what appeared to be an unconscious state".

"The boys have been able to, [due to] some ingenious things on their part and a bit of bravery, recover him in 30 metres, which is beyond normal free diving," he said.

"But they've managed through some actions of their own, to which they should be commended, been able to grab him and bring him back to the surface ... but sadly, it was too late for their mate."

Sergeant Harrison said the four men were from south-east Queensland.

"They're all good mates and have been fishing and free diving for a little while," he said.