+1 for Ocean Quest. They do two weekly “fun” dives Thursday night and Saturday as I recall. Good shop but not downtown. Also Edge in North Van is a good group do not know their schedule. A trip to Naniamo is pretty easy from downtown Vancouver and is recommended. Whytcliff is a very easy and accessible dive site - and worth doing. There are other sites further up the highway to Whistler as well. Porteau Cove is a marine park. Not much else close in as you are on the Fraser river delta and everything close by is sand and mud. You really need to go to Vancouver Island or go north up the mainland coast (or south toward Seattle) to get to good diving on the mainland.
Good point about Nanaimo. If you like wrecks there are 3 cool artificial reefs (two of which I worked on in the Navy)
Book with these guys Home | shepherdcharters.ca and walk on the Nanaimo Ferry. Their boat is docked 2 minute walk from the ferry terminal. Easy-peasy