The slide is built within a rock outcrop (manmade I'm sure). The only part of the slide you can see is the hole coming out.
Question about boat ride between hotels, this is something you need to request from the pilot of the boat to make sure he know you want to go to the other hotel. They don't always stop if they don't know someone wants them to stop.
You won't see many adults going down it unless there is a child begging them to go. I went down a few times and it was fun.
DG