This is the largest island in the Chain group off Oak Bay, although it's still pretty small. It's part of the Oak Bay Islands Ecological Reserve. I've done a few dives around the nearby Chain Islets. Some of them were ok and some were disappointing. So far, I've looked for spots that show a steep drop underwater to deeper than 30 feet or so. There's a tiny rock near the West side of Great Chain Island that has a drop to 40' deep or so off it's West side. I took my boat here for a dive on June 8, 2014. I normally wouldn't bother at this time of year because of the plankton-bloom poor visibility, but I had heard a recent report of decent visibility at nearby 10-Mile Point so I decided to give it a try. I put my anchor up on the rock and swam down through a screen of feather boa kelp. I keep wanting to call it "ankle-grabbing kelp" since it's the most frustrating kind to swim through in my opinion. Once away from shore, visibility was around 15-20 feet. I swam West towards the steeper area. The bottom dropped down in step-like rocky reefs to about 35-40' deep. The vertical faces of the rocks were covered with large urchins and giant barnacles. I was hoping for walls of plumose anemones, but I only saw 2 or 3. There weren't many fish either. There were some kelp greenlings, a copper rockfish, an Irish Lord and the usual small sculpins. The rocky steps ended in a flat pebble area that was covered with more urchins in places. I was diving on a "good current" day. The Race Passage current table was only showing around 2 knots, but the current here was almost too strong to swim against. I kept seeing dark shapes charging towards me out of the corner of my eye, but they were just masses of broken-away kelp being swept along by the current. I tried swimming down the flat slope at the base of the reefs. I managed to reach 45 feet deep, but there were no more rocky areas. I swam back up towards my boat and saw some small patches of encrusting hydrocoral on the rocks. Back on the surface, I noticed that my zodiac had developed a slow leak from banging against the sharp barnacles. The wind had also picked up and it was a wet ride back with the waves spraying up in my face.
My curiosity has been satisfied and I don't think I'll be diving here again.