This was a tough one. I've experimented with different configurations of the track with different water physics, but the three underwater segments proved difficult due to how you tend to bounce on the water when at high speed, while the speed also tends to be limited when underwater, which isn't exactly fun to drive.
I'm also still not happy with the track. There are some elements that I think I've nailed, but then there are others that I would much prefer to start from scratch on. Unfortunately, I have no more time to fix things because I've got to submit this now. Ah well.
Still, it was an interesting challenge, and I do intend to reuse some elements to create a new map in the near future.
PS: Block mixing with the new water blocks is great!