I have made a tall tower (nerf pole) which is 1x1 and about 50 blocks tall (works with any height). I then put a boat at the top of it, pushed it off and quickly sat in it.
What I expected to happen was - I thought I would either die or get out of the boat normally.
What actually happened was - I landed without taking any damage, and when I got out it teleported me to the top of the nerf pole.

Steps to Reproduce:
1. Build a nerf pole
2. Put a boat at the top
3. Push the boat off and quickly get in it.
4. Get off of the boat at any time and it will teleport you back to the top.

This video shows the bug:
https://www.youtube.com/watch?v=jGSOSbyeRek