You don't have to make a reservation, but cruises do often sell out (especially on the weekend) so you might want to keep that in mind. As long as they're not sold out, you can buy tickets at the dock starting one hour prior to the time of the cruise.
No, you can show up about 30 minutes prior to sailing and purchase a ticket.
Yes unless you arrive there early, if I remember correctly. It's been a while, so I apologize if I am incorrect.
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