I had Hatherspur in a different continent, she brought 3 Galleons, declared war and her units attacked my coastal city the same turn from inside the Galleon!

And she shouldn't be able to do that because....? I don't see a bug.

That never happened in warlords

That's only because the AI wasn't good enough. But it's not a bug, you can (and always could) do the same. Your units get a 50% penalty if they don't have the amphibious promotion but you can use any unit for an amphibious assault, as far as I know.

Did you have an open border treaty, she entered your coast, declared war and then invaded? If that was the case, then it is a bug, if not, it's just improved AI..

Read the new Civilopedia, there's a tip that says: the AI now knows how to perform amphibic assaults, so guard your coastal cities.. (or something along those lines)

I did not have open borders. She declared war entered my teritory and attacked instantly.

I did not have open borders. She declared war entered my teritory and attacked instantly.

Then I'm afraid you were a victim of the new and improved AI.. Time to rally to your defences or, if you prefer, load an old savegame and take precautions.. ;)

Yep - just the improved AI! :D