Water Land is nominally and oxymoron, it’s also the first world to really keep players from advancing. I’ve discussed my long standing fears caused by level 3-3 before. Swimming is such a different mechanic from jumping that I still struggle to get to the castle.
Most interesting is the nature of the islands on the east side of the map. Those islands represent Japan. No, really. The castle is where Kyoto would be. Kyoto being where Nintendo headquarters is. Naturally then the king looks like Mario. It’s just perfect. Read more here.