This is about verse 56 in surat an-Nisaa: --- As often as their skins are roasted through, We shall change them for other skins that they may taste the punishment.---
It is a fairly recent discovery that our skin contains nerves, that we feel heat and pain with. Without the skin we do not feel it.
Hundreds of metres beneith the surface of the oceans there are "inner waves". And when scientists studied these waves, they found that it is actually an ocean beneith the ocean, so they called it the "Deep Sea". In the Deep Sea, it's completely dark, so dark that Allah made the creatures there without eyes/eye-sight [? sic]. They use other senses (like the bat) to find its food and flee their enemies.
Verse 40 in surat an-Nur: Or (the state of a disbeliever) is like the darkness in a vast deep sea, overwhelmed with waves topped by waves, topped by dark clouds, (layers of) darkness upon darkness: if a man stretches out his hand, he can hardly see it! And he for whom Allah has not appointed light, there is no light.
In Tafseer Ibn Katheer it is mentioned that Qataadah (rAa) said that the word lujjiyy means 'ameeq and it has been translated here as vast deep. Note, this citation has been omitted from the online tafsir.com, but I've found it in the Arabic original.
Here is an interesting link about the different layers. It has information about the creatures living there and the scientific names of the different layers.
The first thing the human race noticed when it started to explore higher altitudes and the outer space, was the tightening/constraint of the chest/lungs, because of the lack of oxygen the higher we rise in space.[---]
And whomsoever Allah wills to guide, he opens his breast to Islaam; and whomsoever He wills to send astray, He makes his breast closed and constricted, as if he is climbing up to the sky.--- (Surat al-An'aam:125)