So River Race is kind of an autoscroller - the boat won't rubberband or anything, it reaches the end point at the same time every time, so the fastest 'intended' time is a 2:12, maybe a 2:11 if you get early hits. But if you're fast enough collecting missiles, you can risk a bumpy road to set up a faster kill that saves 3 seconds. I got a segmented 2:08 this way:

That's really cool, bro. I'll try to test it