Baby turtles appear black on soul sand, mud and 8 layers of snow.
They clip inside of the block and are able to avoid collisions and clip through walls in this state (MC-208869)
Linked issues
relates to 7
MC-208869
Baby turtles get stuck inside of soul sand, mud and 8 layers of snow
Open
MC-249229
Light levels in the F3 debug menu aren't accurate when standing on eight layers of snow
Open
MC-267935
Items on top of soul sand or mud will be rendered black
Resolved
MC-245416
Baby turtles suffocate on soul sand
Resolved
MC-139631
Light levels in the F3 debug menu aren't accurate when standing on soul sand
Open
2 more links
Can confirm in 1.18.2.