The chill of the Ice Abyss Waters is far more aggressive than on land.
Xia Hong had already experienced this when he developed the Wuyuan Waters.
On land, humans can at least use fire and clothing to fend off the cold to some extent. If you reach Cold Resistance Level, you rely on the restructured Skin Membrane to resist the external cold air and cold light, so there's basically no fear of the cold during the day.
But not so in the waters!
As soon as you enter the waters, fire and clothing are rendered ineffective.
Moreover, the Ice Abyss Waters are covered by transparent hard ice all year round, which in normal circumstances should insulate against the external chill. But let's not forget, most of the chill in the Ice Abyss originates from that sun in the sky. What it projects down is cold light; in other words, the source of light is the main source of chill.
