This page is all about the Frozen OceanEdit
Far east; on the easten edge of the map, need at least a cobolt drill to penetrate the Mythril ice.
Underwater almost always. Frozen Ocean kicks off with a long swim down through the unbearably cold water to the unbearably cold ocean floor, where you will find a small underwater shelter with a few somewhat large rooms connected with narrow corridors. There is also an underwater greenhouse on the right side. From here, there is a small shaft that penetrates the ocean floor and leads to a beautiful underwater cavern with stunning crystal shards and ambient music. This underwater cave system leads to loot, pit stops, and even a tunnel leading to an entrance to the Hallowed caverns. The frozen ocean is where you fight the Sorrow.
When to comeEdit
I came after defeating the Rage and exploring the Wyvern Mage's fortress. I also had Cobolt upgraded armour and a Cobolt Zweihander and the wand of frost II. I had those items and I found the Frozen ocean quite easy.