A few weeks ago I took a ferry trip to Bainbridge Island. The island itself isn't all that exciting, but the trip from Seattle by ferry only costs $6.70 return and is well worth doing just for the ferry experience.
Bainbridge Island does have a main street which caters for tourists with a few coffee shops, book shops and various souvenir shops, but otherwise it is best to take a stroll along the shoreline. Unfortunately like much of the Seattle area, people are allowed to own property right down to the waterfront, so it is not possible to stroll along too far (more than about 2 miles or so) before you hit private property. This is a shame because otherwise it would be quite a scenic walk.
The car queue for the trip back to Seattle. Some folks probably do this every day.
The ferry has two sections at the bow (front) where passengers can stand up and feel like they are hovering over the water. One of the sections is shown below.
The trip back is best done on a sunny afternoon because there is a spectacular view of the city that is perfectly illuminated by splendid sunlight. The return trip was probably the highlight of the ferry experience for me.