 Tidal water loading of a spring balance

A mass above a sufficiently wide estuary experiences additional downward gravity when extra water is present. Approximating the tide as a plane slab of density $\rho$ and added thickness $h$ gives $\Delta g=2\pi G\rho h$. A linear spring with initial extension $x_0=mg/k$ changes by $\Delta x=(m/k)\Delta g=x_0\Delta g/g$. This isolates direct water attraction; it omits finite shoreline geometry, buoyancy, structural motion and terrestrial tides.