Okay... This is silly... I just wanted to visualise how the speed of water waves on
shallow water varies with the depth. The position of the cursor changes the depth
$h_0$ and the wavenumber $k$. The dispersion neglects surface tension, i.e. using the
standard $\tanh$ dispersion relation
\begin{equation}
\omega^2 = gk\tanh(kh_0)
\end{equation}