How early should I actually get to the port?
Later than your instincts say, and earlier than your check-in window suggests you can get away with.
Most lines now assign you an arrival window and enforce it. Turn up two hours early and you will stand outside a terminal that has no intention of letting you in. Turn up at the end of your window and you walk straight on, because everyone else panicked and came early.
The time that actually matters is all-aboard, printed on your boarding pass. It is not the departure time — it is meaningfully before it, and it is the one deadline on the whole holiday that will not wait for you.
Ports vary wildly in how painful they are. If yours has a quirk — a terminal that opens late, a drop-off that backs up for a mile — post it. That is the kind of thing that only exists in people's heads.
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