The incident happened as the Spirit of Vancouver Island was pulling into the Tsawwassen ferry terminal in Delta, south of Vancouver.
A passenger on the ship, Graydon Gibson of Victoria, says the woman fell from a passenger deck of the ship and he saw her flailing about in the water.
He says the ferry turned around and the crew quickly launched a rescue boat to pick up the woman, who was later taken to hospital.
It's not known why or how she plunged into the water, but Cpt. Don Lessand of the Joint Rescue Co-ordination Centre in Victoria is crediting the Spirit of Vancouver crew for their fast response.
He says a rescue boat was about to be sent to the scene, but never left the dock because the ferry crew recovered the woman so quickly. (CFAX,CKAY)