So I turned on water with trains lying around, and although this is a kickass glitch, just wanted to alert you of it. If they are running around and have velocity, then if in water, they come off the track and keep their velocity in the water. This got me thinking that not only could this be used for trains, you could make a track for boats to follow, you could make a bus line that ran automatically, you could make a cablecar or skilift.