text: In the table below, the dispersion relation ω = [Ω(k)] between angular frequency ω = 2π / T and wave number k = 2π / λ is given, as well as the phase and group speeds.
  Deep water corresponds with water depths larger than half the wavelength, which is the common situation in the ocean. In deep water, longer period waves  propagate faster and transport their energy faster. The deep-water group velocity is half the phase velocity. In shallow water, for wavelengths larger than twenty times the water depth, as found quite often near the coast, the group velocity is equal to the phase velocity.