A man in his 30s and two 9-year-old boys were left clinging to a boat in Mandurah on Saturday after their vessel started taking on water.
Around 4.20pm the 5 metre fibreglass vessel started sinking after being swamped by a large wave.
The three were clinging to the bow of the vessel which was the only part out of the water.
Around 4.40pm, a hand-held VHF radio floated free from the vessel and the man was able to grab it and make an emergency radio broadcast. This broadcast was received by Peel Water Police and Mandurah Marine Rescue.
Approximately 20 minutes later, an EPIRB in the vessel floated free and this enable rescuers to hone in on their trio's position.
Police Air-Wing and Water Police officers along with Mandurah Marine Rescue were dispatched. Officers in the police helicopter spotted the trio in the water about 10 metres west of the Dawesville Cut.
Peel Water Police officers pulled the trio from the water and provided first aid.
They were taken to shore and then conveyed to the Peel Health Campus for treatment of hypothermia and jelly fish stings.