The incident began Friday night with a report of an armed robbery underway at a credit union in downtown Nelson.
The police station is about three blocks away, and officers were soon giving chase to the suspects.
Officers finally caught up to one of the suspects, a man, about 20 kilometres to the west on a bridge in the Bonnington Dam area.
Nelson Police Sgt. Janet Scott-Pryke said that rather than surrender, the suspect jumped off and fell about 10 metres into the water below.
"At that place, he was not complying with officers' commands and subsequently jumped over the bridge and landed approximately 30 to 40 feet below," she said. "He did sustain injuries and he has been taken into custody, although [he] was at the hospital for treatment."
The man's injuries were deemed significant enough to warrant the involvement of B.C.'s Independent Investigations Office, which looks into matters where police are present or involved when members of the public come to harm.
Nelson Police also arrested a woman, and said she is suspected of being an accomplice.
Police would not say whether they believe this robbery attempt is connected to a string of increasingly tense robberies of banks, pharmacies, and convenience stores in the region.