This bug report is a parity issue with Java.
Summary:
This bug was fixed in the Java version MC-198805.
There is a floating pixel that appears near the guardian's tailfin.
Steps to reproduce:
Place the guardian / elder guardian in an enclosed space with water.
Take a look at its tail texture.
Observed results:
There will be a gray pixel near the tail that is not even attached to the tail.
Expected results:
This pixel should not be there.
Image:
[media][media]
Fixed in the first 1.17 beta, by looking at the texture files.