To be honest, I think this issue is pretty self explanatory, but just for reference, here's an example:
https://www.dropbox.com/s/98flinr37ug8sht/Water%20Slab%20Glitch.mp4?dl=0
Environment
Windows 10
Java 1.8.0_91 64bit
AMD FX-8370 Eight-Core Processor
NVIDIA Geforce GTX 970
The link doesn't work.