A man who had been in the water for two hours was rescued after a dramatic rescue operation in Guilderton late yesterday afternoon.
In a busy day for rescuers, the 32-year-old man was washed off an inflatable raft when the Moore River sand bank broke.
He was one of four people who found themselves in trouble when the bank broke.
The man was in the raft near the entrance to the ocean with another man, 31, when they were caught in the washout of the bank breaking and taken a few hundred metres offshore.
The 31-year-old managed to stay in the raft when his friend fell out. Both were wearing flotation devices.
The raft washed up about 500m north of the river mouth, with the 31-year-old man still holding on.
A police spokeswoman said the Water Police Coordination Centre organised a marine search and rescue operation, deploying a police helicopter and a rescue boat from Two Rocks Volunteer Sea Rescue Group.
"The 32-year-old man had been in the water for about two hours when the police helicopter located him about 500 metres offshore," she said.
The rescue boat headed to the man in the water, picked him up and took him to shore where he was treated for hypothermia.
The man was taken to Joondalup Health Campus for further observation.
Also caught up in the Moore River incident were two teenagers who were riding body boards when the river bank broke.
One managed to get out of the water immediately but the other, a 15-year-old boy, was washed further out.
He eventually found his way to shore where he was assessed by St John Ambulance.
He was not injured.Police said this incident served as a timely reminder for people to take care when undertaking water based activities; and to ensure that they carry the appropriate safety equipment, where possible.