U-511's skin is cold?

That's because that girl's skin is metallic, yeah?

That girl—

They said it is a nano-metal skin mimicking Abyssal Ships' outer shell, created by the unique technology of those overseas.

Moreover, her blood might have been mixed with Abyssal genes too.

Thus making it become like an ultra-low temperature coolant.

is already pretty much an Abyssal Ship.