Help, trying to remember a book I borrowed once. The highlights I remember were: space ships powered by elemental water. A repressive government that keeps a tight rein on the supplies of fuel for ships. Travel through their version of hyperspace involves navigating music and lights. There's a goal to find a hidden planet (Earth) that is locked away by a "distortion field" that makes hyperspace navigation to it all but impossible. Finally there was a scene where rebels/pirates land on a planet/moon that is a source of elemental water. The ice under a ship cracks and the ship falls through. Every part of the ship is dissolved except for the special "silvered" keel that drives the ship. I think that scene may have been on the cover. Any hints would be great.