= Neutral buoyancy
{title2=$\rho_{\mathrm{body}}=\rho_f$}
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<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 $0.10\ \mathrm m$ <cube> of <mass density> $1000\ \mathrm{kg\,m^{-3}}$ in the stipulated <water> has <mass> $1.000\ \mathrm{kg}$, so both <forces> are $9.81\ \mathrm N$.
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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