A woman, two infants and and two teenagers were taken to hospital on Thursday night after a pontoon capsized in Mandurah Estuary.
About 7.20pm, 13 people were on-board the pontoon on the Mandurah Estuary when the pontoon took on water and capsized.
Everyone on board ended up in the water but were rescued by nearby vessels.
Their ages ranged from from four months through 45-years-old.
Peel Water Police and Mandurah Volunteer Marine Rescue assisted.
Two infants, aged four and six months, two teenagers and a woman were taken by ambulance to the Peel Health Campus as a precaution.
The Department of Transport Marine Safety are also investigating.
A woman who’s believed to have witnessed the incident said the vessel was swamped by a larger boat.