Variation of the dimensionless relative wave celerity as a function of dimensionless wavenumber in the range 0.01-1000, and Froude number in the range 0.1-10. To the left the celerity is asymptotic to the kinematic wave celerity (Seddon celerity: 0.5), and to the right to the dynamic wave celerity (Lagrange celerity: 1/ Fr).