Basically when you die in single player or if your on a server on hardcore mode, or if your on a server you can do /gamemode spectator, It for some reason I see right through the world the thing you can see are entities like chest in Minecarts, Minecarts, all the Minecraft mobs, anything that is defied as a entity, but they are all glitched out. It's quite frustrating, I tested with other people logging into my server or going into their own single player world and they get the same thing so I don't think its just some people... at least I don't think so