Influence is the ability of a ship to claim buoys and score points in a blockade. Each ship type has a different number of pirates needed for influence. On subscriber oceans, this many pirates aboard must be subscribers. This number is not the same as the number of pirates a ship needs to effectively function in a blockade.
If the minimum number of pirates for the ship type has been met, the ship will influence blockade flag buoys in the following pattern (verify). Since there are 6 different influence diameters, 6 ships icons have been used in this graphic to represent each diameter. A ship icon indicates that any ship with that influence diameter, or greater, would influence the square if the ship were located in the center of the pattern.