A 24-year-old man has vowed to always wear a life jacket after a lucky escape from a boating accident off Queensland's Sunshine Coast.

The Coolum man fell overboard from his 4.5m runabout around three kilometres off Mooloolaba on Thursday.

Key points: Coast guard recommends safety lanyards and lifejackets when boating, especially alone or at night

Coast guard recommends safety lanyards and lifejackets when boating, especially alone or at night A commercial fisherman, who saw the runaway boat, says it's a miracle the man was seen and rescued

A commercial fisherman, who saw the runaway boat, says it's a miracle the man was seen and rescued Mooloolaba Coast Guard was able to bring the out-of-control runabout under control

As well as not using a life jacket he wasn't wearing a safety lanyard that, when attached between the skipper and the ignition, automatically stops the motor if the skipper gets thrown out.

'Sickening' find

Commercial fisherman Bill Gilliland said he felt sick when he came across the out-of-control boat circling at high speed.

Mr Gilliland was heading closer to shore as conditions were too rough further out when he noticed something wasn't right.

"I saw a boat in the distance going around in circles and I continued to watch it and I thought after I saw it do about 40 circles in the same spot, 'There's something wrong here'," he said.

"So I went over to the boat and there was no-one in it.

"I called the [Mooloolaba] Coast Guard immediately and it felt rather sickening when you just don't know where to look.

"It's a horrible feeling. You don't know how many people were in it, how long it has been going around in a circle for.

"You have no idea where to start."

One lucky boatie

Coast Guard Mooloolaba intercepted the boat in choppy seas. ( Supplied: Coast Guard Mooloolaba )

Mr Gilliland said the driverless boat continued doing circles at high speed when he approached another boat nearby and asked for help.

"They said, 'Well, it's your lucky day mate, we just picked him up'," he said.

"It was my lucky day that the first boat in the distance had the bloke on board, so it was a miracle."

Mr Gilliland said he could only speculate what had led to the incident but, with the number of sharks and rubbish around, being in the water was the last place he would want to be.

"The conditions must have been a lot rougher than he expected and obviously something went wrong and he popped over the side," he said.

"He was just so lucky it's unbelievable. It's his lucky day. He's a lucky, lucky man."

'Shaken, but not disturbed'

Coast Guard Mooloolaba commander Bill Asher says attaching a safety lanyard is one of the precautions boaties should take out on the water. ( ABC Sunshine Coast: Kylie Bartholomew )

Coast Guard Mooloolaba commander Bill Asher said the rescued 24-year-old man was unhurt and "shaken, but not disturbed".

He was taken back to Mooloolaba for a police interview, but declined media interviews.

The man told the Coast Guard that he would wear a life jacket from now on.

Mr Asher said, with seas up to 1.5m at the time, it was pure luck that the out-of-control runabout didn't hit him.

"It was a lucky escape," Mr Asher said.

"The lucky part is that he didn't get hurt getting thrown out of the boat.

"If he would have been knocked unconscious or something he would have drowned.

"He was lucky it was a good day with lots of other boats out there but, if it was a bad day and he was on his own, three kilometres is a long way to swim back in again."

The commander said the situation was "most uncommon" but had happened before.

"It was only a few years ago up in Cairns the skipper of a mothership fell out of his dinghy," he said.

"The dinghy was going around in circles and came around and ran over him and he drowned."

Threat to shipping channel

The rogue runabout was found near Murphy's Reef, adjacent to the busy shipping channel into the Port of Brisbane. ( ABC Sunshine Coast: Kylie Bartholomew )

While the man was safe, the rogue boat was adjacent to a busy shipping channel where cargo boats were waiting to enter the Port of Brisbane.

It was also a threat to other fishing vessels in the area.

With this in mind, the coast guard deployed its large rescue boat to bring it under control.

"Water police advised us they were going to put up a helicopter and we were tasked to go out and see what we could do," Mr Asher said.

The coast guard used their vessel to 'T-bone' the boat, which straightened it up and reduced its speed.

"We were able to drop a line over the back of the boat onto the outboard motor and tie that onto our boat so we could slow it down," he said.

"When we got it to a manageable speed, we got someone on board the boat and cut the engine."

Safety reminder

The safety lanyard cuts the motor of a boat when it's yanked out, such as in the event of a person being tossed overboard. ( ABC Sunshine Coast: Kylie Bartholomew )

Bill Gilliland, the skipper who found the rogue boat, said it was a confronting safety reminder.

"It certainly shakes you up a bit and makes you start to think about your own bad habits, that's for sure," Mr Gilliland said.

A spokesman from Maritime Safety Queensland (MSQ) said it was "strongly recommended" that skippers of all boats have a safety lanyard attached to their wrist or life jacket.

"This ensures the engine cuts out the instant the skipper is not next to the engine, such as in a man-overboard situation," the spokesman said.

"By taking the additional simple step of clipping on your safety lanyard you can prevent a mishap becoming a serious incident."

MSQ also recommended a life jacket when boating alone or at night.

According to the department's figures, in the 25 years to 2017, 135 recreational boaties drowned or were presumed to have drowned in Queensland waters.

Only four were known to be wearing a life jacket.

Coast Guard commander Bill Asher says the life jacket on the left is less restrictive but not as effective as a floatation device as the one on the right. ( ABC Sunshine Coast: Kylie Bartholomew )

However Coast Guard commander Bill Asher said "very few people" actually wore life jackets — even those who could not swim.

"We have had to go out and rescue people who have come out of a boat or couldn't swim," Mr Asher said.

"Very few people wear life jackets — I don't know whether it's a comfort thing or a macho thing."

He said there were legislative requirements for wearing them, but it was also common sense.

"For any vessel under 4.8m the operator has to have a life jacket on; that is a rule for crossing the bars," he said.

"Once you cross the bar you can take that life jacket off and just sit out there, and in calm conditions people get away with it 99 times out of 100.

"But when the seas are up, it's just a good idea to put them on."