I believe that the BtS SDK made it so that ships can only move through Forts which are adjacent to water tiles. I am pretty certain that this is a change in the SDK, although I do not know exactly where.
There is a slim chance that the change might be to the game engine instead of the DLL, in which case there is really nothing a modder could do about it.
I would be shocked if there is a way to change this fundamental aspect of Fort behavior using only python. If you want a work around, it would be relatively easy to use python to change a land tile to coast in order to allow the forts on either side of it to work as canals.
How important is this to you?
If you really want to do it, you will probably have to find the code, change it, and compile a custom CvGameCoreDLL.dll.
There is a slim chance that the change might be to the game engine instead of the DLL, in which case there is really nothing a modder could do about it.
I would be shocked if there is a way to change this fundamental aspect of Fort behavior using only python. If you want a work around, it would be relatively easy to use python to change a land tile to coast in order to allow the forts on either side of it to work as canals.
How important is this to you?
If you really want to do it, you will probably have to find the code, change it, and compile a custom CvGameCoreDLL.dll.