Quote Originally Posted by Ibn-Khaldun
First thing, why would you ever recruit a full stack fleet??
I agree, even a half stack of Biremes seems to get the job done. Boats seem to get experience a lot faster than armies, so just take your training against fleets with one ship or so and you'll be ready to face most fleets. Even so, I don't even recall the AI putting many ships into one fleet; I think that they like to have many small fleets, rather.

Sorry for going off topic, but the question has been answered anyway.