You've got lots of options, then, Trisk.
Auburn is an industrial region full of factories and blue-collar workers, but there are some AA security rated neighbourhoods here (Auburn proper, and Lake Wilderness).
Bellevue is where the cream of the crop lives, with several AAA, AA, and A rated districts, such as Hunt Point, Rosemont Beach, Inglewood, Yarrow Point, and Bellevue proper. Some of these would likely be waterfront properties (but these might require Luxury lifestyle if you ask me)
Downtown is the cultural center, again with plenty of AAA and AA neighbourhoods; Matthews Beach and North Beach seems like credible places for water access.
Everett has an actual ship yard, and Norma Beach or Edmonds should have access to water while being AA rated or above.
Fort Lewis obviously has a significant military presence, so might be out.
Puyallup is land-locked, if you don't count the Puyallup River.
Redmond has access to water, but is a hellhole.
Renton is landlocked.
Snohomish might have access to water for all I know, but it's always been the woodlands of Seattle as far as I can remember.
Tacoma houses the Tacoma docks, and an extensive coastline. Ruston is a AAA rated neighbourhood close to Point Defiance Park, and has a LOT of waterfront properties.
Outremer is a collection of islands, so could potentially serve as your own personal castle ground...

Also, remind me not to shack up with Johnny Juju.