I'm playing on 1.16.5 (release 1.10.1). Animals will disappear and reappear sporadically when underwater, and only the parts of them that are above the water will show. This is only happening with the mobs from this mod.

very big bug....
try removing any water-related mods(if any)

try set graphic to fabulous ,i think it had something to do with that cause' i had same issue but if i enable fabulous in graphic setting, it fixed.