Thank you. I should have said that before; this kind of developer response is rare, and should not go unnoticed. I am far too used to clicking upvote buttons. Good to know new ship units start in the city they are built in; it's been a while.
I missed this part before:
"I have thought about making units auto-recalculate a new path to the destination tile (if one exists), so that you don't have to manually manage the unit yourself. Do you think that would be preferable?"
That sounds good to me. If unexplored areas are treated as traversable, it could also enable semi-automated coastline exploration by clicking on an unexplored tile that the sea unit probably cannot reach.
Which brings up a thought; I don't know if you want to add automated exploration? This could enable fully automated coastline exploration by treating a land tile as unexplored. The sea unit would try to move through the unexplored tiles to reach the target, revealing more of the coastline. Depending on tile visibility, this might require adding a few more fake unexplored tiles, so the bot thinks there might be a path?