The search for a man missing from Boundary Bay at Great Lake has resumed at first light this morning.

Police believe the 50-year-old Sheffield man was taking a break ashore while on a solo fishing expedition, when his boat floated away.

The man appears to have swum out to the vessel in an attempt to retrieve it.

A bystander alerted authorities about 12:40pm yesterday, after the man disappeared from view.

Police have located the boat and returned it to shore, however the man remains unaccounted for.

Police maintained a presence at the scene overnight, with search and rescue ground crew, local officers, marine vessels and the Westpac Rescue Helicopter currently searching the area.