Drop something into a fluid and it pushes fluid out of the way. The fluid pushes back with an upward buoyant force equal to the weight of the fluid displaced — Archimedes' principle, found in a bathtub around 250 BC.
Whether it floats comes down to one comparison: density. If the object is less dense than the fluid it floats, sinking only until it displaces its own weight. Denser than the fluid, and weight wins — it sinks. Equal, and it hovers: neutral buoyancy, how a fish or submarine holds its depth.
Push a floating block under and the buoyant force grows — the deeper it goes, the more it shoves back. That restoring push is what makes a cork pop up.
Steel is nearly eight times denser than water, yet ships float. Hollow the steel into a hull around a huge pocket of air and the average density of the whole vessel drops below water. Same steel — new shape — and it floats.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.