Emergency crews are scouring the sea off Mackay for a fisherman who has been missing since late Thursday.

He is one of three men who were aboard a vessel near Creal Reef in the Coral Sea when an EPIRB was activated about 80 nautical miles offshore about 8.10pm.

Queensland Police said a search began involving sea and air crews.

One man was found clinging to the overturned boat early on Friday. The 44-year-old from Grasstree Beach was retrieved by marine rescue crews about 7am and taken to Mackay Base Hospital in a serious condition.

A second man, a 43-year-old from Bray Park, was found by the rescue helicopter just after 11am.

He was flown to Mackay Base Hospital for treatment. He remained in hospital on Friday afternoon, and was assisting police.

The search continued into the afternoon for a 41-year-old man, also from Grasstree Beach. He has not been seen since late Thursday and police hold serious concerns for his welfare.

Queensland Police said investigations into the cause of the incident were continuing.

Boaties and other recreational water users have been asked to immediately report sightings to police.