Look at how this fish tank at Maryport Aquarium appears to narrow very quickly, far more quickly than perspective would allow. I've been working on a ray diagram:
Light from each end has to bend to reach the same eye, meaning for the angles of refraction that r2>r1. This means that the ray with angle r2 is showing you a piece of the back wall that is further back than the distance between the two normal lines on the front wall. I added the dotted blue lines with the idea that the brain can't cope with light bending and makes it so that what we see is as if the light had gone straight. This accentuates the effect described above.
