In the terrorism context, the delivery boats are not meant to be seen at all, but just to drop their Islamikazi crew off "over the horizon". The terrorists then use GPS etc to home in on the nuclear power plant or other target in small nearly invisible (at night) rubber boats.
And terrorists will not use anything as splashy as a Mk V, they will use a fishing boat etc.
It is true that terrorists won't be using anything as nice and sinister looking as a MK V. Being stealthy isn't always neccessary, though. Sometimes obvious is better. Use the expected to do the unexpected.
Civilian ships- and ports- are accustomed to flotsam and jetsam type of craft around them, and so there isn't a need to be stealthy to approach. The terrorists can easily afford the kind of craft to get in close, IF people aren't more suspicious. Figure out the routine and mimic it, and you can go just about anywhere.
Or there's Port Access Plan B. Hire a stripper from the local terrorist watering hole and entertainment center, and have her drape herself across the deck of a small boat in a manner sure to interest a mariner. Fly a large US flag. Add some fishing rods. It would be like being given the key to the port... the locals might escort you in close but the last thing they would suspect is Islamic terrorism.