Slitherine

If I have a province, the land military unit are created in the provice capital.
I always thought that the same is for the naval unit so i was always developing the province capital in order to create naval units but I have a vague memory of my first match where my capital was Naples and my Ship builder city was Tarentum.

Can you confirm that for the naval unit they are built in the region qwhere to choose to build them ?

By default that should be the provincial capital region, unless there is no harbor in which case that would be another region

Yes at the end I did some test.

Taranteum had the most advanced shipyard (already built when I conquered it), able also to build the heavy warship.
Naples was my provice capital with a shipyard able to build just till the medium warship.

I "ordered" a mix of heavy, medium and light warship. The next turn i found my fleet scattered across the two cities: the heave in Tarentum, the rest in Naples.
At the end I had to transfer my capital in Tarentum to avoid this in the future.