Passenger injuries after the crash at Horizontal Falls in the upstate ranged from cuts to the head to broken bones, Royal Perth Hospital surgeons said.
A 49-year-old woman was taken to Broome Hospital with spinal injuries but was later airlifted to Jandakot Airport in Perth.
Horizontal Falls is an iconic tourist destination where a swift tidal current weaves through two narrow gorges of the McLarty Range at Talbot Bay.
Twenty-six tourists and two crew members were on board the vessel when the incident occurred at 7am on Friday.
Regional Police Commander Brad Sorrell said several people were thrown overboard and injured.
Hospital staff were put on standby from Friday morning and busy with multiple surgeries and psychological treatment for patients aged 46 to 70.
Three patients have now been discharged and doctors expect everyone involved to make a full recovery.
The investigation into what went wrong is ongoing.
The company involved insists its vessel did not capsize, dismissing claims by police and witnesses that passengers were thrown overboard.