A seven-year-old boy is in a critical condition after clinging to debris with his father and a friend, for more than six hours after their boat capsized off the Sunshine Coast early on Sunday morning.

Police have confirmed the boy, Julian Hohnen, his father Maike Hohnen and Stephen Jeacocke were not wearing life jackets and were sleeping at the time the boat began taking on water.

Key points: Police say a distress call was received just after 1:30am saying the boat was sinking

Police say a distress call was received just after 1:30am saying the boat was sinking A major search and rescue for the boat found the trio in the water more than six hours later

A major search and rescue for the boat found the trio in the water more than six hours later The boy is in a critical condition while the two men are suffering from hypothermia

Police say a distress call was received just after 1:30am saying their 5.2-metre boat was sinking off the coast of Caloundra.

A short time later, a second distress call was sent out, saying they were in the water.

7yo Julian Hohnen has been transferred to Queensland Children's Hospital in a critical condition. ( Facebook: Maike Hohnen )

The trio was spotted by the crew of an anchored off-shore tanker, which notified authorities, and the two men, aged 48 and 39, and the young boy were rescued just after 8:00am.

Queensland Ambulance said the boy was being flown to the Sunshine Coast University Hospital in a critical condition, while the two men were being transported by marine rescue with hypothermia.

The boy has now been transferred to the Queensland Children's Hospital, where he remains critical.

Kristy McAlister from Queensland Ambulance Service said they were rescued just in time.

"It's very fortunate that the three people were found when they were …they're all very lucky," he said.

Ms McAlister said rescuing the child could have made his condition worse.

"It's always a delicate operation when you're winching a patient that's potentially suffering from hypothermia, because as you winch them out of the water the wind temperature can also decrease the body temperature further," she said.

Police first received the distress call just after 1:30am. ( ABC News )

Another volunteer, Rod Ashlin, took the first distress call from the driver of the boat and said he had done "the right things".

"The car was in our car park and the trailer, and they actually logged on and said where they were going so we did have some details about them," he said.

"The only thing they could have done better was that in a mayday situation in a perfect world, the first thing you do is give your position so that if your batteries go flat, we know where to look."

Coast guard volunteer Ian Hunt said it was not clear why the boat started taking on water.

"The only message that the radio room got was that the boat was taking on water fast … that was the last call we got," he said.