Which Assassin's Creed game first introduced naval warfare as a major gameplay feature?

Assassin's Creed III first introduced naval warfare as a major gameplay feature in the series.

Released in 2012, the game lets players control naval missions as Ratonhnhaké:ton, commonly called Connor, during the American Revolutionary War. Connor commands the ship Aquila in battles against enemy vessels in the Atlantic Ocean and along the North American coast.

These missions include sailing, maneuvering, firing cannons, and using heavier weapons against opposing ships. Naval gameplay was initially one part of Assassin's Creed III rather than the entire structure of the game.

Assassin's Creed IV: Black Flag is often incorrectly credited as the first game with naval warfare because it made ship exploration and combat much more central. Black Flag expanded the feature substantially, but Assassin's Creed III introduced it to the franchise first.