According to the man, the realm he and his people live in is extremely inhospitable to life, forcing all that develops within it to accommodate to the extreme environment, for example, although clearly humanoid, it seems like the sapients of this realm are not humans, or are at least a completely different species of humans who have thoroughly evolved to survive.
The reason he and the people before him had been skinned alive was actually not intended as torture, it was because otherwise, they would easily survive being thrown down here, indeed, their skin had developed into a sort salt armour, turning completely white and growing solid, yet flexible bits all over the body, which allowed even a mundane member of their group to resist being submerged in highly concentrated waters like here.