This glitch consists of a skulker and a boat. Have a shulker in a boat and then either drop from a ledge or just sit on the ground and once you are near or on the surface just getout. The shulker will then get stuck in a block, if you mine the block will go away but the shulker stays. From there you can have pistons go through the shulker or push blocks into it etc. The shulker will not teleport at all in any circumstance and just stay. you can even hide the shulker in blocks and it will persist to shoot through the blocks around it and the block in it. I have abused this as a sentry in SP and it works. The shulker can be hurt and killed.