There are at least a hundred park and fly lots near SEA and the cruise industry has several very large lots at the pier. I saw RV's in both areas this summer, but do not know about hookups. The "cruise" lots are
expensive, even for a car, so you could probably do better finding an RV Park and paying the weekly rate. The private park & fly lots near SEA are less than ยฝ the cost to park a car as the cruise ship lots and there are many transportation companies to get you to the pier.
Bob & Betsy - USN Aviation Ret'd '78 & LEO Ret'd '03 & "Oath Keeper Forever"
2005 HR Endeavor 40PRQ, '11 Silverado LT, Ex Cab 6.2L NHT 4x4, w/2017 Rzr 4-900 riding in 16+' enclosed trailer in back.Where the wheels are stopped today