Sarge?
Maritime security has been a back-burner thing with DHS since the kickoff. The main thing was to get the airports secure once again.
Think of it this way: How many business commuters travel by container ship? Or by river barge and tug? The vast volume of human passengers travel by commercial air, and with the assets in place post-9/11, that was the high-payoff action to take.
Now that the commercial skies are more secure (not a 100% solution, but deterrence goes a long way), more assets can be tasked, and greater emphasis paid, to maritime security. Assets in place will be augmented first, therefore, before new things get tried.
UPSHOT: Now we're getting more rumblings about the ports and the ships. It's because there's more notice. And the enemy watches the increase in activity, too. They're seeing greater awareness and vigilance, so some targets might get bypassed as being too solid to take.
It's a massive chess-game, Folks. And we have a few Grand Masters on our side, too.