Okay. Traveling via self-catapulting rock is cool. Inventing super jumps to skip puzzles is cool. Dropping a chicken wing on the ground in below-freezing lands and it turning into a frozen chicken wing is cool. There are a lot of little cool things in The Legend of Zelda: Breath of the Wild.
But little cool things can come together in more and more complex or inventive combinations. Thus, placing Octo Balloons on a raft to turn it into an airship, as YouTube's BeardBear has done.
If you wanted to fly even fast, you might be able to use the same "motor boat" trick that you can use to make your raft move faster in the water, but your flying machine probably won't be stable enough.