The above is a commonly performed but often overlooked mission for the Coasties.
While the majority of the 73 Coast Guard 87-foot Marine Protector patrol boats are based at SAR stations around the country to perform coastal interdiction, fisheries patrol and rescue missions, there are a few whose bread and butter is fleet protection.
You see, while speedy little Navy patrol boats manned by bluejackets may be ideal, the fact that the Coast Guard is mandated to perform domestic law enforcement without that whole Posse comitatus thing getting involved is the key.
The Navy even pays for four WPBs, Sea Dragon (87367) and Sea Dog (87373) at Kings Bay; Sea Devil (87368) and Sea Fox (87374) at Kitsap, to ride shotgun on SSBNs headed in and out on deterrent patrols. While most 87s only have two M2s forward and a 9-man crew, these up-armored Maritime Force Protection Unit models mount a third remotely controlled mount and carry up to 15-man crews.
Then of course there are the seldom talked about Navy-owned, USCG-manned and marked 64-foot Special Purpose Craft Screening Vessels stationed at major naval bases (Norfolk, Bangor, etc).