The bug

The player can reel in their own vehicle / ridden entity using a fishing rod. This does not make any sense physically and apparently can also be exploited to fly if performed fast enough (e.g. using an auto-clicker).

The expected behavior is that if the player tries to reel in the fishing rod, and it is hooked into one of the player's vehicles, no motion is applied to that vehicle.

See Reddit post: Goodbye world

How to reproduce

1. Bind the "Use Item/Place Block" action to any key
2. Switch to Creative mode (so the fishing rod does not break that fast)
3. Put a fishing rod in your hand
4. Start riding any vehicle
5. Look downwards at the vehicle
6. Hold down the "Use Item" key bound in step 1
   The vehicle you are riding starts moving because you are reeling it in