Try a cargo container at a major US port. ...The title relates to a threat from the sea. AQ obviously doesn't have traditional warships - they have plans to use cargo ships instead - not for conventional weapons either.
AQ has lots and lots of plans.
Most of them are red herrings.
Pulling off a nuclear attack with a container is a little harder then some would have us believe.
Assuming AQ has access to nuclear material. Which is a big assumption given the way we moved in on countries that couldn't adequately secure their nuclear programs.
AQ is not likely to get their hands on nukes in the near future, and if they had any prior to 2002, they would have used them by now.