It was a terrible idea, with even worse execution.
Splash is a relatively intense ride (for a castle park) and this version doesn't have a villain or any tension (which is needed on a flume) - think of West as the local example and the voice lines it plays leading up to the final drop (when they're working). I'd imagine little kids would be scared shitless with that drop that comes after "Lets get you to the party". Prime example of mismatching the story with the ride layout.
Just a case of a terrible IP match with the ride type, it looks like princess and the frog was shoehorned into the ride when the IP and story should be integrated ito the ride layout. The IP and the story they were trying to tell have been a much better fit for a ground-up gentle dark boat ride, I think Lilo and stitch would have been a much more suitable refit for Splash.