Wannabe is right about Sunrise for Wolf Eels. But that's Gig Harbor, not Seattle, and not a whole lot closer than Anacortes, the gateway to the Juans. (Sunrise is really close to the Narrows, and you have got to watch the tides.) The problem with diving the Juans is that you absolutely have to have a boat. Also, the 13-21 of July has some nasty steep tidal exchanges which will make for some tricky currents up there (although they do get a bit better towards the end of your planned trip). If you can get away, I'd suggest you try to get over to Hood Canal and dive Sund Rock and Octopus Hole, two dives within a few miles of each other, both marine preserves. There's a mated pair of Wolf Eels (Fred and Ethel) at Sund, and Octo all over the place. Currents are never a real big deal over there, and there is a great LDS close by
Hood Sport & Dive . And hotels are all over the place.
Closer to Seattle you can dive Edmonds Underwater Park, another marine preserve close by where you are guaranteed to see the biggest Ling Cod you have ever seen. I've never seen an Octo or Wolfie there, but there's plenty of other stuff to pique your interest. They've been dropping junk (old boats, conduits, an old dry dock, construction debris, etc) there for decades.
Alki is a popular dive site. You can see plenty of stuff there. I haven't dived it much because I hate crowds, but I've heard of sixgills being sighted there along with the octopus and wolfie stuff. It's a popular place for OW dives, so you may have to dodge classes, but it is worth it.
Here's a great link for local sites:
Eric's SCUBA Page . It's not updated anymore, but the site reviews are pretty good. Ignore the one about Octopus Hole, they never found the wall and dove on a tire reef that's close by (yawn).
You can't get near the water around here without seeing a seal. But don't be expecting to see one from underwater, that's pretty unusual. I'd definitely recommend the Juans for that.
In Tacoma there's a dive at the Les Davis Fishing Pier. Lots of OW classes are done there as well. There are two nice reefs, one at about 40-50 feet, and another that drops down from about 70 feet. Lots of stuff lives on these, including the 'Big Three', but it's not a preserve and Ling season just ended, so I doubt you'll see many of those. While in Tacoma, you might think about diving Titlow. It's in the Narrows, so you'll have to watch the currents there as well. If you decide to dive there, make sure you check with someone local (I can help) about timing your dive.
I guess it really boils down to your schedule. If you're stuck close to Seattle you'll be spending most of your time at Alki and Edmonds. If you can get away, make the treck to the Canal and do Sund (and I'll give you the scoop on where to get the best authentic Native Americal smoked salmon I've ever had--ingredients: salmon, salt, smoke). If you can get to Gig Harbor, do Sunrise (watch the tides).
Let me know if I can be of any more help.
Oh yeah: you'll need at least 7mm. If you have a dry suit, all the better. The water'll be about 45 degrees at depth.
