I recently finished a cruise in Vancouver, and my flight home wasn't for 8 hours.

I highly recommend joining Evo (car share) in advance, then step off your ship, there were three Evo's 30 seconds away, get the audio app (Get Along), tour Vancouver at your leisure using that, then drive to YVR, drop off Evo at Park and Jet. Great option. "Rental" for day is $89.