"Oh that's because Fishman Island is reeeeeeeeeeeally far down and Nami says we haven't sunk enough yet" Luffy explains as he points at Nami who had moved to the helm of the ship.
This is the story of a demon who undergoes a transformation from being a gentle and kind person to becoming a cold and indifferent man. Tom starts out on "Earth" and then merges with his AI and starts his journey in the world of fantasy.