This is a shallow reef sitting out by itself in Boundary Pass that eventually drops down on all sides to over 100' deep. I came here on a SEA Dive charter on Feb. 13, 2022. Conditions on the surface were about as good as they get, with calm water and sun. I swam down East along the South side of the reef. Visibility was a bright 20' or so.
The rocky slope went down to a sandy bottom with boulders about 60-70' deep. Almost as soon as we started descending there was a school of black and yellowtail rockfish. This Southern side of Arachne Reef is in a Rockfish Protected Area, which hopefully will deter at least some people from rushing over to try to wipe them out. There were a few clusters of plumose anemones in the shallower depths, but overall, there weren't piles of invertebrate life on the rocks for a spot that gets lots of current. There were lots of urchins and swimming scallops. I was surprised by all the red slipper cucumbers. Most of them had their tentacles retracted (they go dormant in the Winter just like the orange burrowing variety), but I don't think I've seen this many anywhere else.
We swam back the way we came, but shallower up near the top of the slope.
I swam over the top of the shallow reef (10-15' deep) towards the North side.
On the North side of the reef the bottom dropped down in small walls and ledges. There were lots more plumose anemones on this side compared to the South side. In some spots they covered the walls and valleys in a fluffy field of white. I saw an octopus out in the open. Because of the threatening current and limited dive time, I only explored down to about 60-70' deep.
I think the North side of the reef has much more invertebrate life than the South side. The South side has more fish though (again, it's in a Rockfish Conservation Area so hook-and-line fishing and spearfishing are illegal). If I come here again I'd like to see what the West side of the reef is like.