Coming from the Netherlands, I know they most probably flew in from Schiphol as that is the Netherlands' main airport and Rotterdam/The Hague are both accessible within an hour from Schiphol. Rotterdam/The Hague Airport is no big deal. There is also a direct train from Paris to Amsterdam however.
There is also a huge possibility they visited both cities, as they form a metropolitan area together and are connected easily by train, bus or even taxi. The port task in the preview is probably in Rotterdam, as it has the largest port in Europe and once the largest port in the world.