There are two rails on the drops, which you can see right before you go down and if you look back after the drop. The boat rests on that as it goes down, but that only serves to keep the chain dog out of the way, and protect the bottom of the boats. As far as during the ride, the boat is truly floating. No track below.
So for the hills - the question (as related to my point about preventing bottoming out) would be where do the rails stop??... probably after the boat has transitioned to full horizontal, forward movement again.