Rashi: Gehinom is naked opposite Hashem - He knows and sees all that is inside it.

Ibn Ezra: In She'ol, a hidden place, Hashem does His desire.

Malbim #1: This metaphor is based on parables of early Chachamim, which tell that people attributed divinity to giants. After they died and descended to the depths, they emerged from the water and were born again, they became gods and new creations, in the follies of mythology. The grave is naked - how will they leave to be born again?

Malbim #2: What is in the innards of She'ol and the depth of the water, it is not covered from the orders of the Ma'arachah. There, Hashem could punish Resha'im without changing the natural order!

Malbim: After the body decayed, the Nefashos remain naked without a covering. They will not return to bodies.