Is there anyplace in Washington that you can load your boat full of camping stuff boat out to a remote place and camp? I used to do this all the time at Lake Mead but I don't know where to go around here.
Someplace where the water isn't freezing preferably.
Not really close to Seattle, but we do it all the time on Lake Roosevelt in central WA. There are some great boat-in only camogrounds that have nice docks and bathrooms or you can anchor the boat and beach camp anywhere you can find a suitable beach. Lots of options as its a huge lake
Again, not really close to Seattle...we used to go to the Pot Holes Reservoir near Moses Lake. Sandy beaches, deep water shores, warm water and not many people on the off weekends. The holidays were nuts.
Like Adam said, Lake Roosevelt has boat in camping spots. Water is right around 80 degrees and the further you go up the Spokane river the more butter you will find.