Arcanic Seastorm

There is no natural storm on the sea like the eternal, raging tempests that ring the entire continent of Harokin. Arcanic seastorms, as they have been dubbed, are the result of a rapidfire condensation and violet disruption of environmental arcana. At the very edges of the arcana-consumption effect of titans' long-reaching auras, ambient arcana is regenerated at a normal rate--then quickened because of disparity between its source and the physical reality where it emanates--then rips apart and takes the water cycle with it, shredded into constant rain and heaving waves and drenched thunder.
The arcanic seastorms are almost solely responsible for how impossible it is to reach Harokin from the outside or to escape it from the inside. The frenzy of arcana and its effect on the sea and sky is miles thick, easily able to rend apart even the sturdiest of ships and watercraft. It also leaves a sharp divide in the sealife - the shorelines and tidepools are almost completely cut off from the deeper sea, resulting in an "island evolution" effect for the creatures originally stranded along the land's edge during the Shattering.
If approached from the outside, where ambient arcana is plentiful and relatively stable, a kinvar sorcerer could attempt to harness and calm the arcana within the storm. It is possible, albeit challenging, to do so. But as one travels into the tempest, one loses one's own arcana to the osmotic effect of the titans' aura--and thus one loses control again of the storm, becoming stranded in the middle of the worst of it. Death follows swiftly and unkindly to those who, over the milennia, have tried to breach the impassable wall of arcanic seastorms.
In certain areas, where an ocean trench might allow an exceptionally deep passage beneath the disruption of the storm, it is possible to duck the tempest. To do so, however, requires a physiology that no kinvari possess, and not many endemic animals find it worthwhile to risk getting that close to such savage riptides.