Space has little meaning in the Sea of Chaos. Matter, distance, and gravity are in constant flux. Lands and creatures appear and dissolve within moments. There are waves of lightning, streams of lava, and hurricane winds constantly shifting direction. While the elements may be mundane—unlike the surreal vistas of Xoriat—size has little meaning. A thousandfoot-long dragon turtle might appear, try to swallow travelers, then become an island.
Travel through the Sea of Chaos is driven by pure will. Travelers must impose the concept of motion and distance on the environment using great mental focus, while also protecting their vessel from both the destructive forces and from being transformed. The DM could reflect this journey with a series of ability checks, or simply require the adventurers to have a captain and vessel capable of making the trip before they try to cross the sea. Regardless, to successfully travel, the adventurers must know where they want to go; without a destination to serve as a conceptual anchor, they’ll quickly crash on a random Shifting Island.