The RCMP are searching for a missing swimmer at Barbour Pond, near Keels, on the Bonavista Peninsula.
They were called to the pond Wednesday at 4:30 p.m.
Four people had gone out swimming and were returning to shore when one, a 78-year-old man, went under, police said.
The man was not located by the RCMP and ground search and rescue volunteers on site.
The search resumed Thursday, with help from the RCMP's underwater recovery team.