steps

1.make a tower of a non falling block  stone lets say

2.place 3 sand on the stone tower

3.place a boat on the 3 sand

4. somehow place 3 more sand on the boat most likely making a tower to the side

5. break the stone tower but the one block the sand is on 

6.break the last stone block

what happens is 2 sand should fall and there should be a floating tower of sand with a boat

what's meant to happen is the whole sand tower should fall to the ground and not float

video link https://www.youtube.com/watch?v=i3qBrfAKoB4