This is what my daughters came up with.
First I showed them the new water ride at Center Parcs Elvedon Forest, the Tropical Cyclone.
Star decided to call our water ride The Rivengre. The ride would be all the colours of the rainbow and have lots of twists and turns. You can choose which colour you wish to ride down, but the colours will change on the way down to the pool. Each person would ride on an inflatable animal, from a crocodile to an elephant. Boo added that she would like the ride to be very very fast, little daredevil that she is. The ride would be like a helter skelter, but with several lanes. At the end it would be like a bumpy slide, the kind you get at fairgrounds, before you plunge into the pool, hopefully still on your inflatable animal.
Here is a picture board we put together of The Rivengre, and the original drawing by Star.