Good info from MedSailor.
One anchorage I haven't seen listed yet is Utsalady on the north side of Camano Island. There is a public launch there for land access, the depth is right for anchoring but there are several private moorings in there that take up the prime real estate.
The dock at Coupeville gets shallow on a minus tide as does some of the dock space at Cornet Bay.
While the currents in the Swinomish Channel aren't predicted, we have found that when the water is high, it's flowing north and when it is low, it's going south. The slacks aren't predicted and the level of the Skagit River have an influence. It's just been dredged, so it's supposed to be navigable on minus tides again.
If there is a significant north breeze, you can find yourself in the mud at low tide if you're on the Hope Island buoys. They are set very close to the shallows and rely on the tidal current to hold you off far enough not to get stuck. We've seen several boat run into the mud on buoy #2 from the west while making their approach to that particular buoy. We like #1 from the west, but we pull the buoy ring all the way up to anchor
roller and we won't tie up to it if the wind is out of the north. Skagit Island has buoys nearby, but we don't care for them at all. One goes underwater at high tide, the other gets too close to shore for our comfort.
The float just outside Deception at Rosario can be nice, but is also a shallow one. We used to tie up to that one a lot with some of our earlier boats. The park closes down at dusk then you have the whole place to yourself. The floats and buoys at Bowman Bay are in the line
of fire from the west swells from the straits. We've had some nice times in there and some bad times. The floats rock around so much that the picnic table legs have worn hollows out of the float decking.
Langley is a neat little spot. We've pulled in to the float on winter trips. There is room outside to anchor
, but we've not had to do that.
In Holmes Harbor, there is decent anchoring at the south end at Freeland and a county park for land access. There is also an anchorage on the west side of the bay at Honeymoon Bay ?, but I'm not sure if there is beach access there. I've not anchored there, just seen a lot of boats moored there on private mooring balls.