I know Phil is not exactly rigorous with what is written, but we still have to assume only what is exactly written. You can consider them knights, but if they are not adjacent then they can't attack.
I think that the card would be clearer if it did say "consider" instead of "count."
But Duchy of Ferrara (83) uses similar language: "A white token in Venice counts 2X in all Battles."
While one can imagine that the Knights might use ships to participate in Crusades anywhere in the Mediterranean (and that that could be part of the card's ability), I'm not aware of any thematic reason that Duchy of Ferrara would extend use of a Venice Token geographically.