The Canadian Coast Guard says it received a call about a woman screaming for help after her kayak overturned on Friday night.
It asked for assistance from the MV Quinitsa, which operates on a route from Denman Island to Buckley Bay.
At the time the ferry was unloading passengers and vehicles at Denman Island, and within minutes the crew launched a rescue boat.
The woman was saved about one nautical mile north of the Buckley Bay terminal and transferred to an ambulance on shore.
B.C. Ferries spokeswoman Deborah Marshall says coast guard officials called the crew later to thank them for their swift response and credit them with saving the woman's life.