Yes that is correct Jeff. Actually most flume rides (and recently the disney rapids rides) with drops dont need the water to make the baot go down the hill since it does roll along a track. On regular flumes namely Intamin log flumes and Arrow Splashdowns (since i have worked both)there are reagular "road" or load wheels that hold the weight of the boat and guide wheels that keep it centered. Niether of these rides really have that steep of drops so the wheels stay in contact with the track at all times. At the bottom a "flap", if you will, covers the track allowing the wheels to go between it and the track to prevent hydroplaning.
As for the water, the drop area is "ridged" with either small metal flaps or bumps that disturb the water flow. if they werent on there the water would appear clear and wouldnt look as dramatic. This is similar to the reason these rides have pipes or long pieces of wood underwater to disrupt the water flow, giving it a rougher or more rolling appearance.
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"ok everyone go ahead and pull down on your shoulder restraint so you feel nice and stuck!"