Rescuers will continue searching from the shore into the night for a diver missing off Dawesville.
Water police, fisheries workers and volunteers today searched more than 300sq km for the 38-year-old who failed to return to his group at Dawesville yesterday.
"The search operation will continue through the night, which shore based searches continuing," a police spokesman said in a 3pm update on the operation.
"The search operation will continue tomorrow morning."
Emergency authorities were told the diver had failed to resurface about 5km off the Dawesville Cut about 1.30pm yesterday.
A police helicopter continued with a search of the area until just after 9.30pm last night.
This morning, the search resumed with a police helicopter, a dive team on police boat Cygnet V, a vessel from Peel Water Police and four volunteer rescue craft from Mandurah Water Rescue Group, Rockingham Volunteer Sea Rescue Group and Fremantle Sea Rescue.
Boats from the departments of transport and fisheries also joined the search today.
It is understood the missing diver was on a boat with up to four other people.