[quote]Can ghosts hover over water?[/quote]I can't imagine they would. Using in-game effects, we see that the Ghosts anti-gravity simply displaces the water, meaning it'd sink once it got far enough out in a body of water. [quote]Also, how do spartans go through such long missions without eating or sleeping?[/quote]They do eat and sleep. We never see this because it's not relevant to the story or gameplay. Still, Spartans are able to remain active for several days of continuous service.