Which Assassin's Creed game was the first to feature a fully controllable ship as a major gameplay element?

Assassin's Creed III was the first Assassin's Creed game to feature a fully controllable ship as a major gameplay element.

Released in 2012, Assassin's Creed III introduced naval missions in which the player commands the ship Aquila. These sequences include steering, positioning the vessel, firing cannons, and managing combat against enemy ships.

The game is set during the American Revolution and follows Connor, also known as Ratonhnhaké:ton. Although naval missions form only part of the campaign, their reception helped inspire the much larger maritime focus of Assassin's Creed IV: Black Flag.

Black Flag is therefore often remembered as the franchise's definitive pirate game, but it did not introduce ship control to the series. Assassin's Creed III established the system first, while later games expanded it with open-sea exploration, upgrades, and extensive naval combat.