I've heard of a few people diving here, but it's not a popular local site or anything. Most people have probably never heard of it. I always assumed you needed a boat to dive here, but on one of my drives to Mill Bay, I noticed that it's pretty close to shore. Tanner Rock is a "mini-pinnacle" about 200 meters offshore between the Mill Bay ferry terminal and Mill Bay (on the West side of Saanich Inlet). There's a short, narrow, dirt road winding down to a small point that looks like the remains of an old jetty. There are groups of pilings clustered together off the South side of the point. Straight off the point is Tanner Rock which is exposed at low tide and is topped with a navigational marker and piles of harbour seals. I came here in mid-March, 2006. The point is a large dirt-mud area with room for as many vehicles as you like. I strapped on a compass and swam out to the rock underwater. A gentle slope of gravel with the usual Mill Bay orange plumose anemones and sea stars led down to a flat sand-silt bottom 30 feet deep. After a bit of a swim (it wasn't as long as I expected), the rocky reef popped up without much of a warning. There were rock walls and piles of boulders leaning on each other. There was a surprising variety of invertebrate life that you usually don't see in Saanich Inlet. There were clusters of colonial tunicates that I'm used to seeing in more current-swept areas (Pender Island, Beaver Point, Arbutus Island, etc.). There were also clumps of giant barnacles, orange "sea peach" tunicates, cup corals, plumose anemones (white and orange), a swimming anemone, and the usual assortment of seastars. I was hoping to see some seals underwater (there were at least 10 on the rocks and several heads bobbing on the surface), but I only managed to see one tearing away in panic on the edge of visibility (20 feet vis.). For some reason harbour seals on the Island seem to have social phobia when it comes to divers, unlike the mainland seals which fight each other for the privilege of tugging on your fins. I didn't see many fish either which I guess is understandable for a seal hangout. There were a few kelp greenlings and some terrified-looking juvenile copper rockfish hiding in the crevices. There was a fairly large school of perch swimming in the open though. They must pay protection money. The rocky area bottomed out at around 30 feet on all sides. I swam out past the reef farther into the Inlet. There was a steep slope of sand-gravel that I followed down to around 90 feet. I didn't see any rocky reefs down here, just more orange plumose anemones and seastars so I swam back to the shallows. On a chart, this slope leads down to 300 feet pretty quick. Back near the marker, there was an area 15 feet deep with suprising masses of cup corals in the cracks and little overhangs. During my swim back to shore, I had a look at some of the pilings. They were covered with more plumose anemones than I expected to see in Saanich Inlet. It was quite a sight with the sun shining down through them. Between the pilings and the shore there was an old speed-boat-type hull on the bottom with an octopus den in a hole in the middle. To sum up, I was hoping for something a bit deeper and maybe some seal photos, but I was actually pleasantly surprised. I might even go back.
I came back hoping for some underwater seal photos. When I arrived, I could see around 40 seals crammed on the rock (low tide) and a few more swimming around in the water. I figured I had it made until I put my face in the water and saw the 3-foot visibility. I swam out a bit and descended. I saw the sandy bottom below me and then I went right through it. It turned out that there was a layer of brown water from 10-25 feet deep. Visibility was only 1-2 feet here. I kept swimming, expecting to bump into a seal at any moment. Eventually, when descended below 25-30 feet, visibility opened up to around 10 feet. There were a few clouds of stirred-up sand which told me that seals were around, but I didn't see any.