I've always thought it was interesting that they balance a flat disk on top of the turtle.
If you think about it, clearly the
shell of the turtle was intended to be the Earth by whoever thought of the turtle analogy to start with.
So they were clearly aware of the curvature of the Earth, but they just didn't take that all the way to the idea that the Earth is a sphere, so they made the analogy of a turtle swimming through an ocean, with the shell itself being the ground and the ocean being what the turtle is swimming through.
^ I mean ... this is a traditional depiction. Can you see the redundancy here? I can just imagine the originator of this idea going "no no you people completely missed the point!".
"There's a shell-shaped thing on the back of the turtle, what stops it falling off. I know, we need
elephants!" No you don't, because turtles by definition already have a shell-shaped thing on their backs, it's just called a shell. Maybe there were in fact two different traditions here, one that the world was on the back of four elephants, and the other that the world was on the back of a turtle (more accurate in some senses), so they just decided to smoosh both explanations together in the stupidest way possible.
Note, that the ocean must be on the top shell here, otherwise the elephants would drown, so the turtle must be swimming through a
different ocean. So now not only do you have two shells, but you have to have two completely different oceans: the Earth's ocean, which is carried by air-breathing elephants, and the turtle's ocean, which is below the level of the elephants. If you just get rid of the elephants then the top plate merges with the turtle's shell, and you only need to posit one ocean, which also keeps the turtle afloat.