French submarines in NTW

Well with Steam driven sailing ships and Observation Balloons being available for
Napoleon Total War. On the basis that prototype steam ships were being developed
at the time.
Then its reasonable to ask whether the deployment of submarines might be possible
for the Napoleon's french navy.
If developed in sufficient numbers, it would certanly clear the channel of the Royal
Navy although its range and effectiveness might be limited ?
Is it historically possibe. Well yes it is.

http://en.wikipedia.org/wiki/Nautilus_(1800_submarine)

Anyway another novelty to go with the steam ships. Lol.

from the wiki page you linked

"The French navy had no enthusiasm for a weapon they preferred to think suicidal for the crews"

I think its unlikely to be honest, and i would rather not see it ingame myself