The province of BC operates the largest ferry fleet in the world. The fact that so much of BC's population is scattered on a large number of islands off the mainland requires that such a fleet be in place. The ruggedness of the coastline makes this, in some cases, the only economical mode of travel.
The sizes of the ferries vary greatly depending on traffic and location. Some trips last mere minutes (Albion - Fort Langley or to/from Barnston Island) to two hours (Vancouver to Vancouver Island Victoria/Nanaimo). On the northern routes there are schedules that cover days of travel and provide the only access other than by air (mainly floatplane).
Taking a trip on the ferries can be an excursion all by itself. The most scenic route is the Vancouver to Victoria one (Tsawwassen - Schwartz Bay) since it makes a course around some of the southern Gulf Islands. The highlight is the passage through Active Pass where the tides can produce exciting rushes of water. You can park at the terminals or take a local bus to them and get on as a foot passenger for a return trip. Most people include a day trip to see the sights of Victoria.