Neutral buoyancy means a fully immersed body's upward buoyancy equals its downward force from gravity. For a body of fixed volume in a constant-mass density fluid under a uniform gravitational field, this occurs when its mean mass density equals the surrounding mass density. A cube of mass density in the stipulated water has mass , so both forces are .
Ideally it can remain at rest at any depth for which it stays fully immersed and clear of boundaries. Raising or lowering it changes the absolute pressure, but neither its displaced volume nor the difference between the vertical pressure forces. There is therefore no vertical restoring force toward a preferred depth in this model. Neutral buoyancy is a vertical force balance, not a claim about resistance to tilting or about a compressible body whose volume changes with pressure.
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Neutral buoyancy is a state in which an object neither sinks nor rises when submerged in a fluid. This occurs when the buoyant force (the upward force exerted by the fluid) acting on the object equals the weight of the object (the downward force due to gravity). In practical terms, when an object is neutrally buoyant, it will remain suspended at a specific depth in the fluid without ascending to the surface or descending to the bottom.