Shag Harbour UFO incident

At about 11:20 p.m. on 4 October 1967, Laurie Wickens and four companions near Shag Harbour, Nova Scotia, saw a low-flying lit object descend towards the water, hearing a whistling sound and a bang; other witnesses, including RCMP officers, saw the object about 250–300 metres offshore, its lights still visible on the surface before it sank.

Believing an aircraft had crashed, the RCMP, local fishing boats and a Canadian Coast Guard cutter searched within the hour. They found a large patch of yellowish foam but no survivors, bodies or wreckage. By morning the Rescue Coordination Centre in Halifax had confirmed that no commercial, military or private aircraft was missing, and a priority telex to Canadian Forces Headquarters logged it as a "UFO report". Navy divers of Fleet Diving Unit Atlantic searched the seabed for three days and found nothing.

The Department of National Defence records, now at Library and Archives Canada, make it one of Canada's best-documented UFO cases. No explanation has been established.

Sources: Department of National Defence documents (1967) · Wikipedia