Which game first introduced playable naval missions to the Assassin's Creed series?

Assassin's Creed III first introduced playable naval missions to the Assassin's Creed series.

Released in 2012, the game includes missions in which Connor Kenway commands the ship Aquila. Players steer, accelerate, turn, and fire cannons while fighting other vessels in the waters around the North Atlantic and the American coast.

Naval play was a significant addition to Assassin's Creed III, whose main story is set during the American Revolution. The feature proved popular enough to become a much larger part of Assassin's Creed IV: Black Flag, which built its open world around Caribbean sailing and piracy.

Black Flag is therefore often remembered as the series' definitive naval game, but it was not the first to include naval missions. Assassin's Creed Rogue and later games expanded the mechanic further, while Assassin's Creed III established it in the franchise.