It’s the only con I know of to have a cruise. Misha hosts it and there are 100 tickets available each year. You get a 3 hour boat ride, dinner and dessert, and Misha spends some time at each table.
There was also Comic Con at Sea (a 7-day cruise) a couple months back and I know there are at least three companies planning future cruise cons. One of them has a 3-day Catalina Island cruise planned.