WA Police divers are searching Black Diamond Lake near Collie after a man in his 30s failed to return to shore when swimming there on Christmas Day.

A group of people raised the alarm at about 2:30pm when they realised a member of their party had not returned to shore.

They asked a member of the public for help, who in turn contacted police. 

Officers from Collie Police rushed to the scene, where they patrolled the lake's perimeter to try and spot the man. 

Members of the public joined the search on paddleboards, while a police helicopter also provided aerial support. 

The search is continuing on Monday, with specialist police divers in the water. 

Ferguson Road has been closed to the public.

Police have asked people planning on visiting the lake to avoid the area while the search is underway.

Black Diamond Lake is in Allanson, a town on the banks of the Collie River about eight kilometres west of Collie. 

It has become a tourist hotspot in recent years thanks to its clear blue water, which is popular with Instagram users. 

The lake is an abandoned mine site that was decommissioned in the 1950s. 

The Collie River Valley website says swimming in the lake is permitted, but because of the site's past use as a mine, the water has a "low pH level" and "those with sensitive skin should limit their exposure to the water."  

The website also says "the water in places is very deep and can be very cold".