Deep ocean internal waves: What do we really know?

We review the state of observation of internal waves in the light of suggestions that there is a universal isotropic spectrum. The general conclusion is that the data are inadequate to draw such an inference at this time. A universal spectrum is also precluded, since it forbids sources and sinks for the motion. The deviations from homogeneous models are the physically significant quantities, and certain zero-order questions are proposed to study these deviations.