X-ray glitch when boating in cave 2×1

How to track the glitch 

1.mine a 2×1 hole. 2.drink your night vision potion, and place the boat. 3.go in the boat and go slowly  in the wall. 4.don't go to far, or you Will sufficate. Now you Will be able to see the whole cave sytem. You can use your spyglass to check it out. Examples like the one in the video below