Making land tile passable to sea units

[Funkativity]

I'm trying to implement a 'Canal' improvement, something similar to how Forts worked in previous Civ games.

the part I'm struggling with is how to designate the tile as passable to both land and sea units.

it seems possible given that City Center tiles functions this way but I haven't been able to figure out how.

 

[isau]

I'm trying to implement a 'Canal' improvement, something similar to how Forts worked in previous Civ games.

the part I'm struggling with is how to designate the tile as passable to both land and sea units.

it seems possible given that City Center tiles functions this way but I haven't been able to figure out how.

Sadly it seems like this buried under multiple layers of UI and hardcoding. It may be possible, but the developers didn't make it easy. Not sure why, since Canals are one of the most asked for features.