I really liked the top-down 3d of the building phase! The visuals of it really struck me. It took me a minute to put the first piece down but it was straight-forward after that. I'm not sure if the different pieces had different effect beyond aesthetic in this version, but I like the idea!
The sailing phase could have a bit more to it. More obstacle permutations, or some mechanic to mix it up like stabilizing for a big wave. On the technical side there could be a check to make sure certain obstacle set-ups can be evaded, and maybe a timer or distance meter. But maybe it's the point that you don't know how long you'd be on the open sea.