Pikmin 2 is my favorite game in the series so I am a little bias, but I can still admit that the dungeons were poorly executed. Just from playing the demo though, the dungeons of Pikmin 4 feel much better balanced and less cramped. They also seem to not be randomly generated, which will probably make them feel less repetitive. Even exploring the inside of a house would count as a “dungeon” now but it is a very novel experience in Pikmin so I am all for it.
Two fans on a plank with a steering stick are pretty much the most cost-efficient boat you can build. You can try to get creative using a big wheel to make a paddle similar to a steam boat, but in my experience those don’t work very well. Maybe a stabilizer could help.