This tiny "cruise" (also known as the "boat-bus" by Vancouverites) takes passengers from Science World all the way to English Bay. It's more effective than the busses for some trips, and it is really beautiful. You get an awesome view of the skyline. Some people take it to work, and others take it for fun. It's also affordable, and relaxing.
If you can't afford a fancy dinner cruise, this is a great way to see the city (you'll see some locals going to/from work with their bikes), and a fun way to get around. It's a great way to see a lot in a very short amount of time (notably, if you only have a few days in the city, and no car). Plus, who doesn't love boats?
It can close early, so check the weather. It is good for a rainy day; the boats are all-weather.