  Fermi-surface bosonization is used to show that the long-wavelength, $T=0$,
dynamics of a BCS superfluid or superconductor is described by a galilean
invariant non-linear time-dependent Schr{\"o}dinger equation. This equation is
of same form as the Gross-Pitaevskii equation for a Bose superfluid, but the
``wavefunction'' is {\it not} the superfluid order parameter.
