Police divers are currently searching for a man who was last seen at a popular swimming spot near Collie.
The man in his 20s went swimming in Stockton Lake around 3.15pm on Sunday.
Police say the man required assistance but members of the public who were on the shore were unable to help him.
The search is continuing today, while the lake has been closed off to the public.
Stockton Lake is a popular camping spot and was once a mine site before it was filled with water to form an artificial lake.