how would you go about gathering information to a question like : How has the government responded to the threats of maritime terrorism?
I am not sure who you are asking, but I would want to know what methods are being used on military ships and what measures are being taken by civilians. Besides terrorism, there are pirates to worry about. Every ship needs security.
I would spend some time on the US Department of Homeland Security website, which details some of the programs, agencies and personnel involved in protecting the US from another terrorist attack. Next, I would look at the latest edition of the US Statistical Abstract, which is chock full of hundreds of thousands of facts and figures about America and our government.
Besides your obviously great choice to post an eNotes discussion about it (and really is there anything better?), I highly recommend that you access your school library's online 'bookmarks for research'-- academic databases and search engines. I also recommend the Library of Congress as well. If you want more academic and serious analysis, then I definitely recommend searching the academic databases first, and it would not hurt to go in person to the library and ask for some pointers from the librarian. It might feel awkward but could really pay off in the end in terms of saving you hours of futile wandering around those databases. Chances are the librarian would jump at the chance to help you further your research on maritime terrorism and could point you to some very specific material online or in print.
Just poking around your topic, I found this interesting site, Maritime Terrorism, by a man who works for the International Institute for Counter-Terrorism; his site provides both historical context as well as current day concerns.