Glad you enjoyed it so much! The reason it was done that way (specifically, it goes from 25% of the way up to all the way up in the last quarter of the time) was because we didn't want the water to be too visually distracting in the majority of the time playing. By the time it's going up fast, you'd already be familiar with how the room works in most cases, and having the blue over everything makes it a little harder to parse. The water rising faster is also when a water flowing layer gets added on top of the music, for a little bit of extra-fitting ambience :)