It seems like this would have been noticed by people way before recorded history and at every period and place in the world. Objects in pools of water, peering through clear glass, looking at your own legs while standing in a clear stream, having to spear your fish by aiming a bit differently than they seem to be- how would people from different times and places have made sense of this extremely common but strange phenomenon?
The Suda, a 10th Century Byzantine encyclopedia/lexicon, defines "transparency" in the following way:
"They say that something transparent is a nature present in many substances that lets things pass through. When light is not present this thing itself is transparent in potentiality, but becomes transparent in actuality when light is present. Not only are the air and water transparent, but also many of the solid materials, such as moonstones, horns, glass, gypsum, and other things. The celestial material also partakes of transparency and invisibility, such as the fluid of the spheres; for it is completely transparent. Indeed, we see the stars in the firmament through it. Now the spheres are transparent but the stars are not transparent at all, and this is why they get in each others' way. Hence eclipses of the sun, at least, clearly appear to happen when the moon gets in its way."
It is obvious from this passage that the Medieval Byzantines understood that transparent objects were defined by the linear passage of light through them, which naturally would have told them something about refraction. Under the entry for "light" in the Suda, it is written that "light is not a body", so they also understood that light was different than matter, but, from the previous quote, they also knew that it could be affected by it.
Anyways, under the same "light" entry, however, the authors left us with the tantalizing line "Many other things are also argued about light to the effect that it is not a body, things that we have passed over due to our lack of expertise, but that anyone may investigate." This perhaps tells us that the existence and nature of light was hotly debated by Byzantine scholars at that time. Indeed, it is certainly possible, considering the various bits of evidence that exist in Byzantine manuscripts and letters dating from 10th - 12th Centuries.
I will do some more investigating to see if there are any direct quotes regarding refraction through interfaces. I believe I remember seeing one in one of the works of Psellos.