Thanks a lot for your comment, Itooh! *-*
We're really glad that you had fun with this, despite the tricky controls ^^' We needed a way to increase difficulty as the game went on, and the speed growing was the immediate solution. Probably, other choices would have been better and would have avoided the perceived chaos at the end. Learned lesson: the next time we'll make something with a clear end, or a character which the user is happy to see dead wet :P
Regarding the procedural generation, the river is composed and re-assembled as needed with the available pieces. The seamless chain is obtained with a special piece (that we humbly called The Universal Joint - it sounds so stupid now) that's placed between every two sections and graphically covers the minor faults in linking. It's not perfect and sometimes it fails, but we're happy that it worked at least with you!
Again, thanks a lot for your precious feedback and for playing the game, we really appreciated it! :D