Assassin's Creed IV: Black Flag

Ubisoft Montreal's 2013 entry is the one where the naval sections stopped being a side activity and became the game. Edward Kenway is a pirate rather than an idealist, and the Caribbean is a single continuous space you sail across, with the Jackdaw upgradeable from a schooner into something that can take on a man-o'-war. Ship combat is the best thing in the series: broadsides, chain shot, mortars, boarding actions that transition seamlessly into swordplay, and a wind system that means positioning matters. Between fights there is diving for wrecks, whaling, hunting legendary ships and a fleet metagame. The land-based Assassin content is the weaker half, and the tailing missions are the series at its most tedious. But Havana, Kingston and Nassau are dense and readable, the sea shanties became genuinely famous, and the pirate-republic story is the most coherent thing the franchise has written. It is regularly named the best Assassin's Creed by people who otherwise stopped playing them.