Guardians stop being rendered about 16 blocks away from the player (while in water)

To replicate,
find a monument
add night vision effect and wear a helmet aqua affinity enchant
from out of the water the guardians are rendered as you'd expect
in the water they stop being rendered if they're beyond c.16blocks moving in and out of this range will toggle the rendering.

No pictures as there's not much to see 😛 but if you find it difficult to replicate let me know and I'll drop a short video in too.