This was really well done. It's very polished for a 3D platformer made during a game jam, especially one made by one person. The modeling and animation are very charming. Movement felt good with both a controller and the keyboard.
My only real critique is that I would have liked it if the dive had a soft lock-on so it was easier to dive into balloons. It would have made the sections where you jump from balloon to balloon a bit more smooth.
I noticed the fact that the music doesn't loop wasn't in your known bugs list, so I assume that was intentional. That's fine if it was intentional, but I would have preferred if there was music always playing (after you hit the first music trigger) because I was really enjoying it.
I liked the fake-out nature of the ending. I saw the guy and was all "Oh, a boss fight, I wonder how this is going to work." and then the game just ends. I thought it was very funny.
Overall, this was very good! Great job!