I've bought the Citypass Seattle. Do I have to book a seat on the cruise or just turn up there?

Just turn up there 20min before..

Yes just turn up and go into the ticket office, they will print you a ticket when you show your pass and then just join the boarding line and enjoy! 😁🌏

If it's not busy, you can just show up. If it's a busy season, you probably want to go early and get a spot beforehand

U can just show up ..