AI doesn't use work boats. (costum Mod)

[Slave of CIV]

Dear community,

i have made some custom civ's for an Austria related scenario for my own amusement. It's really nothing fancy - i have combined excisting civ's, changed the graphics and called it a day. Overall i am satisified, yet there is a really strange AI behaviour: no AI bothers to make work boats. I have checked the leader.xml and everything seems normal. Screenshots attached.

Could it be that the AI dismisses naval improvements, because the map is - for the most part - a solid landmass?

Thanks for your thoughts in advance!

Best regards,
Olli