In addition to being liable for a civil penalty under subsection (b), any master, person in charge of a vehicle, or aircraft pilot who intentionally commits any violation listed in subsection (a) is, upon conviction, liable for a fine of not more than $2,000 or imprisonment for 1 year, or both; except that if the conveyance has, or is discovered to have had, on board any merchandise (other than sea stores or the equivalent for conveyances other than vessels) the importation of which into the United States is prohibited, such individual is liable for an additional fine of not more than $10,000 or imprisonment for not more than 5 years, or both.