Seacrest Park ... Cove 2, at Alki, West Seattle. Not sure what's to see below about 115, but the techies seem to like it. This is the favorite hangout for the DIR locals.
Mukilteo ... City Park, Lighthouse Point, T-dock ... three different sites in the same general vicinity. A popular site for deep tech dives. Again, I haven't been much below 120 here, but you see lots of technical divers here. Watch for currents at the City Park and Lighthouse.
Three Tree Point North ... Burien. A popular place to go deep looking for six-gills in the summer months. Been down to 128 fsw here, and there are little "junk piles" all the way to that depth, and probably beyond. Was just there yesterday, in fact. Saw some octopus and dogfish, although I maxed out at 89 fsw. You can easily go beyond recreational limits at this site.
Day Island Wall ... Tacoma. An utterly fantastic dive, featuring abundant wolf eel and octopus dens. The bottom of the wall maxes at about 95 fsw, but if you desire deeper you can easily go out past the wall. Time your dives carefully around slack or you'll get swept.
Sunrise, Gig Harbor ... the "wall" (ledge, actually) is between 35 and 65 fsw, but there's lots of interesting structure below that. Been as deep as 90 fsw here, and the boulder field just keeps on going. Lots of wolfies and octos here, as well as an abundance of other marine life. Again, time it carefully or be prepared to deal with serious current. Hiking back up the hill afterward is a serious pain in the posterior ... especially if you're hauling a tech rig.
Sund Rock ... Hoodsport (Hood Canal). A large rock that turns into a steep boulder field and series of ledges underwater. You can get to depths in excess of 120 fsw here. Lots of interesting structure, with wolf eel colonies and other marine life. The downside is that you get to choose to either pay the $15 per diver entrance fee to the site, or do a seriously long hike down a series of switchbacks followed by a fairly lengthy surface swim to the dive site.
Hope that helps you get started ...
... Bob (Grateful Diver)