Barb McLintock with the B.C. Coroner's Service says her office was called in Sunday after the two were found aboard the boat at a marina.
"They did have the engine of the boat running and at some point, then, they were found and one of them was ill and taken to hospital and the other one, unfortunately, ended up deceased," she said.
The service is determining whether carbon monoxide poisoning is to blame.
McLintock said it is possible the engine exhaust somehow ended up in the boat cabin.