The trio were heading back into shore on August 14 with their catch when their five-metre fibreglass boat was swamped by a big wave and started sinking.

"We were trapped under the boat when it capsized," Mr Pries said. "It was lucky the boys had just taken their life jackets off to put their jumpers on, otherwise it would have been even harder to get them out

"And lucky the boat was floating enough to hold onto."

After clinging to the vessel for about 10 minutes, a hand-held VHF radio floated free from the boat and Mr Pries was able to grab it and make an emergency radio broadcast.

This was received by Peel Water Police and Mandurah Marine Rescue.

However, it would have been extremely difficult to locate them as they were about 14 nautical miles off shore, south west of the Dawesville Cut, south of Perth in Western Australia, so Mr Pries made the difficult decision to leave his boys, Nikolaus and Jakob, hanging onto the boat while he dived underwater to find the EPIRB.

"One of my boys said 'Are we going to die dad?' and that was hard to hear, because I didn't even know myself," Mr Pries recalled. "I told them to just hold on."

After getting up the energy and courage to dive back under the boat, Mr Pries managed to find the EPIRB and set it off so that the Police Air-Wing and Water Police officers along with Mandurah Marine Rescue were able to hone in on their exact location.

Peel Water Police officers arrived in the police helicopter and were able to pull them from the water and provide first aid.

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Mr Pries describes seeing the chopper coming to rescue them as a "big relief".

They were taken to shore and then to the Peel Health Campus for treatment of hypothermia and jelly fish stings.

"I'm still pretty sore," Mr Pries said.

"But the boys are back at school. I don't know whether it's hit them yet or not. But school is probably the best place for them - keep them busy and that."

Unfortunately the boat wasn't insured and so they've "lost everything", according to Mr Pries.

"They brought the boat back in and the fish were still in the esky, but that's all we salvaged," he said.

"Everything else we've got is insured; the car, the house, but not the boat."

Despite such a terrifying brush with death, Mr Pries said he's still keen to take his boys out fishing again soon.

"They love their fishing. We've got friends with boats, so we'll try and get out again in a couple of weeks once we've had time to get over what happened.

"Gotta get 'em back on the horse," he said.

WA Police officer in charge senior sergeant Troy Pillage said it was a "great outcome" but also a good reminder for anyone out on the water to carry appropriate safety gear.

"If they didn't have a hand held radio with them at the time the outcome could have been very different," he said.