Much more attention is being given in the press now to the possibility of terrorists using or pirating ships for either smuggling and transportation, or as actual attack vehicles.and points to a Newsweek article as an example, MSNBC Look Out Below-The Terror Threat From the Sea
An intelligence source said the threat should be kept "in proportion." But only last week, a captured militant from a Qaeda affiliate in the Philippines claimed he and other jihadis took diving lessons to prepare for a seaborne attack. A senior Homeland Security official said the administration doesn't want to take "the risk of not doing something to protect against a waterborne assault."
Update: Prior post on Al Qaeda divers.
Update2: The Counterterrorism Blog refers to a James Dunnigan post on the capture of Al Qaeda in the Persian/Arabian Gulf which was the subject of this post which linked to this article from The Peninsula from Qatar, to which I was referred by The Counterterrorism Blog. Small world.