The excess free energy of small-amplitude deformations of a wet "parabolic" brush consisting of polymer chains attached to a solid plane by one end is calculated. The brush is swollen by a good (marginal) solvent. A generic deformation involving both compression normal to the grafting surface and lateral shear is considered. It is shown that the free energy attains a minimum as a function of the wave vector of the deformation, q. A shallow maximum of the scattering function S(q) is thus predicted. The theoretical scattering functions calculated for an arbitrary orientation of the scattering vector are compared with evanescent-wave light scattering data.