Since it doesn't sound like the full nature of existence has been worked out yet, we'll call this one a proposal or brainstorm:
The Jaggerskern, also sometimes called the Grimsea or Sea of Possibilities, is an ocean in the northwesterly realms that surrounds and connects several different anchored shards. Close to stabilized lands the Jaggerskern is safe to ply with fishing craft. But farther out, the waters shift and grow perilous. For the most part the waters of the Skern are dark gray saltwater, but farther out they sometimes...change. In places they turn fresh, or transmute to more exotic liquids like slime or blood, acid, clouds of silvery mist, flowing silt, or even fire. Most waterborne vessels that leave the safety of anchored waters become irrevocably changed and nonfunctional, where they don't simply dissolve or burn to ash. Nevertheless, the Skern is still navigable by airship, or flying mount, or even hot air balloon. Shimmering silver mists swirl and billow above the slate gray seas, intermittently obscuring view above the waters to the height of about 10 to 20 meters. Strange lights, whispers, rushing sounds, tinkling music can often be seen or heard within the vicinity of the mist - believed by scholars to be the echoes of other eras and places filtering through the broken fabric of reality. Strange creatures lurk within the depths. Wild magic storms in particular are a frequent danger to any who would cross the sea.