Boats will glitch a player through blocks when pushed by a piston repeatedly.

Steps to recreate the glitch

1. Create a one block thick flat base in mid air
2. Create a oscillator made by repeators and connect it to a sticky piston
3. Place a object that points out to the piston ( End rod or lightning rods ) on the boat to move the boat repeatedly.
4. Let a player sit on the boat and leave the boat
5. The player should glitch out and fall