After the Blue Boost that's hanging out in the air, you'll hit a bunch of small waterfalls followed by a Tunnel. If you jump on top of the Tunnel, you'll cut you're time in half for that section.

When you get to the part with the three hard turns in a row (left, right, left) you can skip all of this by jumping over the island in between them both. This comes shortly after the part with the docks.

Just after the starting point, you see natives tossing spears. About two seconds after, grind on to the land. You will get in a tunnel, go through a waterfall and find some boost and some airtime.