回复：圣诞节去加勒比CRUISE

Unless you are talking about christmas next year, otherwise it's kind of late to book a cruise. You can still find cabin on most cruise lines, though not likely to find a open berth at a good location, and you are also likely to pay a premier for late booking.

I have booked over a dozen cruises, and I have found that booking online doesn't automatically means lower price. Some travel agents are willing to share their commission with you. So shop around, check with local travel agents, and also check with expedia, travelocity, etc. There are several online websites that deals with cruise only, such as cruiselocators.com, cruisesonly.com, etc. However you need to know that these site tend to have limited customer service. They are great for people who knows what they need and simply need to buy tuy the ticket.

You should also know that most travel agent do not know much about cruising, unless they specialized in it.

Cruising to Caribeen is considered as leaving US. So if you can leave US and come back without new visa, then you can go, otherwise you won't be allowed to embark.
I don't know what F1 visa is, but does it allow you to re-enter US?