Added bad perspective because the rails converge to a vanishing point not on the horizon line. The only way this could make sense is if they were angled skyward instead of being level with the ground, but nothing about the way this is drawn suggests that to be the case.
The further the railway is, not only it gradually disappears, the ground around it turns into sky (or a reflection of it), as if it was a completely separate view.
The railroad doesn't disappear, the water becomes more reflective the more narrow of an angle you observe it from.
You can see it in this picture, or in any body of water in real life.
The water near the horizon is nearly completely reflective and looks like a mirrored version of the sky, while the water closer to the viewer is transparent, and you can see the rocks below.
Yes, it's a stylistic effect, but it mimics a real effect, and the image isn't long enough for it to happen. I'd say the tag is warranted.
Edit: I found another picture, perhaps more fitting, of an actual submerged railroad.
