A person was pulled from the Red River just behind St. Boniface hospital, near Winnipeg's Norwood Bridge, on Tuesday.
The call came in at about 9:45 a.m.
A Splash Dash tour boat, from the nearby Forks harbour, rushed to the scene and was used to rescue the person, described by a witness as a middle-aged man, who was fully clothed.
Gord Cartwright, the owner of Splash Dash Tours, said he noticed a commotion and saw a water rescue technician swimming to help.
So he got one of his boats and went over as quickly as he could.
Police said the person was taken to hospital in critical condition.
Cartwright said if the incident had happened one day later he wouldn't have been able to help. Tuesday is the last day his boats are on the river for the season.