Harbour High Tide
This expansion to the Harbour base game provides new buildings with new special icons, as well as boats - a new card type that helps make purchasing more consistent.
The new building icons include one that allows a bonus action immediately upon purchase, and second-story buildings - which can be built by themselves, or built cheaper as the "second story" to one of your existing buildings, but which then don't count towards the game-end trigger.
The boats can be bought from the center by sending your worker there and spending goods. Later, when buying a building, you may return a boat to the center to help pay for the building.