As has already been mentioned, there's a lot of variety in B.C. diving. And for the most part, you get what you pay for.
Cheapest way to go ... camping/diving at Porteau Cove, on the Sea to Sky highway just north of Vancouver. There's a nice dive park, and if you have a boat there's some nice wall diving just south of the park.
Diving Howe Sound with BC Dive Adventures
http://www.bcdive.com/ is also a reasonably inexpensive option. There are some really nice dive sites out around Bowyer Island ... mostly walls and pinnacles ... and we had a wonderful time there last year playing with a seal.
In Nanaimo the two premier operators are Ocean Explorers and VI Dive Vacations. Both are excellent, and both are reasonably expensive. A less expensive option is to go out on a smaller boat, like Technically Speaking
http://www.tsdivecharters.com/home.htm. My preferred boat in Nanaimo is Sea Kiss (
http://www.vidive.com), because it has an on-board nitrox filling station (you only bring one tank), the boat is spacious for the number of divers it accommodates, and because Ed Singer offers a great overall package for the money. I was in Nanaimo two weeks ago and vis was still quite good (30-40 feet). And although the wrecks are the signature dives in Nanaimo, some of the other dives (like Snake Island wall, Four Fathom Reef, and Jesse Island) are great dives.
The Victoria area also has some fine diving ... and one signature shore dive, the Ogden Point Breakwater. It's a bit of a haul getting out to where the good stuff is, but not too bad ... you just walk along the rocks till you get tired, then backroll into the water and descend. I dove the breakwater last Friday, and vis was 20-25 feet.
Hornby Island also has some nice diving, and a great charter operation ...
http://www.hornbyislanddiving.com/ ... I was up there last July and vis was between 30 and 70 feet, depending on dive site, depth, and what the tides were doing. Rob and Amanda run a first-rate diving operation.
But my favorite (so far) place on Vancouver Island is Barkley Sound. I was there this past week-end and the diving was incredible. The dive sites are mostly pinnacles, with a few walls and reefs. They're covered in life this time of year, and the colors are simply overwhelming. We had vis between 20 and 50 feet, depending on depth, dive site, and tides. Incredible amounts of sea life, with huge ling cod (I saw one this week-end that was easily 150 lbs!), octopus, wolf eels, and more quantity and variety of rockfish than I've seen anywhere else. We went with Rendezvous Dive Ventures in Rainy Bay
http://www.rendezvousdiveventures.com/, and it was great!
Back over on the mainland, try Sechelt Inlet with Porpoise Bay Charters
http://www.porpoisebaycharters.com/. There's not as much sea life as you'll find at Barkley Sound, but the vis is usually pretty good, and the diving is overall very good. I can't vouch for what it'd be like this time of year though ... I was there in February.
I'll be hitting Campbell River/Quadra Island in a couple of weeks, and will post a trip report when I return. It'll be interesting to see how it compares to these other places I've been in B.C.
... Bob (Grateful Diver)