Just because its not a tug, does not mean it has to be an LCAC. It could be a harbor patrol vote like this or any number of things. USN regularly has either coast guard or small patrol boats present when ships are moving. Such as:It looks like a three tugboats, and an LCAC.
A "militia" fishing boat has a high foredeck which is almost as high as its super structure (wheel house), its silhouette is different. While an LCAC has a almost rectangular silhouette made up by forecastle-engine room-propellers housing. While a tug boat has a low foredeck and aft deck with high superstructure at the middle.Even with that kind the silhouette still does not match as the silhouette lacks the raised pilot cabin. More likely its maritime militia.