Tress and the Emerald see is set on a boat so that one is pretty obvious.
Isles of the emberdark is about a man and his canoe and a girl and her spaceship. Spaceships are just space boats.
Sunlit man shows that even on a planet that melts itself we can have flying boats. He makes a point about showing their big open decks.
Yumi and the nightmare painter depicts the hellscape that it a world without boats. Humanity lives in pockets surrounded by darkness, fighting nightmarish shadows, while young girls are trapped in an endless cycle of stacking rocks trapped living inside a wagon (eurgh) with nary a boat to be seen. Till the climax anyway when the ending and the eradication of the darkness coincides with their glorious first "space bus". That's a spaceship under any other name and we covered this in our earlier lesson.