Hey guys. I'll be in Seattle with Douglas Seifert and Simon Rogerson in mid-August to do six-gill sharks, and Douggie and I will have a few days afterwards for local diving in Seattle and Vancouver.
Got advice for who to dive with? We want giant pacific octos, wolf eels, and more.
Any leads would be greatly appreciated!
Bandito Charters is highly regarded for boat diving.
Bandito Charters
As for dive sites, do you want easy or do you want big current dives? In the Pacific Northwest, the current is always a factor and, at some sites, you have to closely watch the tide tables to know when to get in the water and when not to get in the water. Do you like cold water? I hope so, because typical water temperatures in Puget Sound are about 47 degrees, give or take a degree. The viz in August will be better than during the spring algae blooms, but not as good as in December when you usually get the best viz.
Generally speaking, the further north you go in Puget Sound (closer to Vancouver) the better viz you will get. If you are diving in South Puget Sound (closer to Hood Canal and Seattle) the viz is not as good.
Here's another link that may be helpful. You may enjoy reading their reviews of different dive sites.
Northwest Dive News
If you have more questions, just holler 
Ellen