Sea currents won´t work very well in Civ. You see, currents have directions, they´re one-way, they don´t poit every way since they´re vectors.
Understood; nevertheless, having these sea currents in place channels the AI's units (or so I trust) in far more historical locations than letting (for instance) European ships round the northwest African coast before a certain point. Likewise, ships crossing the Atlantic to the New World will be "vectored" towards their historical destinations, e.g., England and France to northeastern North American and Spain et. al. to the Caribe and MesoAmerica.
Best,
Oz