There was the occasional slave-running ship, yes, but I doubt they did business 'en masse'; the profits if successful were good, but besides the prohibition on

There was the occasional slave-running ship, yes, but I doubt they did business 'en masse'; the profits if successful were good, but besides the prohibition on the trade from the US, they had to deal with interdiction by the Royal Navy, and in those days you did not mess with the Royal Navy.