Assassin's Creed is not what it used to be. Yes it has the climbing and the hiding and the jumping off of rooftops to stab up to two people through the skull for the crime of guarding a collectible that you desperately want for reasons that you forgot many hours ago when you took on the task of opening every single frivolous chest of pocket change across the ancient land. But now it has new things added to this tried and tested and then rehashed formula. It's got boats now. Big old pirate boats where your collection of merry buccaneering NPCs sing shanties that you've collected as part of a further collectible gathering ritual and presumably bought back to the ship to teach the men to chant to speed along the journeys ahead. Journeys that will be fast travelled as soon as the option presents itself.
You may remember there being boats in Assassin's Creed 3. They were a small part of that game that was more of a small aside, and an optional one at that, an activity that the game barely seemed to care that you even play. But then people played it and realised that for all intents and purposes it was basically the only shining part in that shit heap of a finale and so the next game became all about boats.