I have a great admiral which has spawned in my harbour district. I cannot transfer him to another city. The option is greyed out.
There is another city close by with a harbour district.
However, the city I really want to transfer him to is in another body of water which is cut off from where he is.
All cities have harbour district and harbour improvements.
I did not choose where he spawned.
Best Answer
As obvious as it is or is not. When the admiral spawns, it was in this case, it was a harbour district. (this was during my first game, so I am now well aware of this shift of units preferring districts when producing)
Once I moved the admiral to a city, I then had the option enabled to transfer to another city.
Much the same as if building a naval unit that if a coastal city has a harbour district, the unit is built there.
Note, you need a city on the coast to be able to move the great admiral.