Man tried CPR on dad before Qld reef death

A spearfisherman was forced to leave his unconscious dad in waters off Cairns in order to swim to safety two days before father's day.

The 24-year-old man and his 56-year-old father were fishing off Arlington Reef on Friday when their boat drifted away in windy conditions.

As they tried to catch up with it, the older man got into trouble.

Sergeant Andrew Ibell from Cairns Water Police said the son tried to resuscitate his father but was forced to make the "heart-wrenching decision to leave" to try and reach the boat.

A commercial vessel named Hero spotted the Gordonvale man clinging to a navigation buoy around five kilometres from where it's thought the men dived.

"He was very distressed obviously," Sgt Ibell said on Monday.

"Water Police went out and picked him up off that vessel (that found him) and brought him back to Cairns to be with his family."

It took crews just 45 minutes to find the father's body.

The boat, which is worth up to $50,000, still hasn't been found.

Sgt Ibell said police expected debris would have been spotted if the boat had sunk.

The vessel was most "most likely still floating out there" and could have travelled as far as waters near Cooktown, he said.

The father and son were relatively experienced spearfishermen.

But Sergeant Ibell said a boat should never be left unattended.

"Or if it is, you've got to have some way of being attached to that vessel so that you can quickly get back on board," he said.

A report will be prepared for the coroner but the father's death is not thought to be suspicious.

Boaties in the area are being asked to keep a look out for the six-metre aluminium vessel, which has a light-coloured centre cabin and black hull with blue sign writing.