William George Caswell was 52 when he vanished on July 21, 1991, during a boating outing on Panache Lake near Sudbury, Ontario. He and his daughter were reportedly thrown from their boat; his daughter swam to shore but William did not resurface. The incident is recorded as a boating accident and he is listed as missing and presumed drowned, but his body was never recovered.

The national record gives his full name and nicknames Bill and Corky, notes he was born in 1939 and described him as about 6 feet 1 inch and 254 pounds with short grey hair, fair complexion and visible dental decay. He was last seen wearing a white cotton T-shirt and tan cotton shorts. No public information indicates foul play or a voluntary disappearance.

Anyone who was on or near Panache Lake around July 21, 1991, or who has information about this accident is asked to come forward.