Still, it does kind of suck that One Piece is slowly becoming more inconsistent in its "science". One Piece was once one of the most "realistic" shonen manga, at least as far as it had a consistent set of laws, realistic relations between characters (for example, the Straw Hats are like one big family), interesting/realistic politics, even realistic sexual themes. It was like a cool Pirate-themed steampunk sci-fi -- I guess it still is, but I feel like the Whitebeard War saga derailed those themes (despite the themes being prominent leading up to the war), and they still haven't been picked up again.
Prediction: van der Decken will throw an enormous axe at the princess. Luffy will deflect it, and it will end up cutting the mangrove roots that give Fishman Island its light.