Internal waves

Rico says his father, a Scripps oceanographer, finally analyzed the 'internal wave' photo (below) sent earlier by his friend Kelley:

An internal wave is another form of a 'gravity wave' ( a disturbance of the interface between two fluids of different densities causes a wave to propagate away from the disturbance). We are used to seeing the air/water kind generated by wind stress. When fresh water floats on top of salt water a disturbance of the interface will produce an internal wave , which will not be discernible as a bump on the top of the freshwater layer. The internal waves in the picture are visible because of the index of refraction difference between the layers of water caused by the local internal bump from the traveling disturbance (acts like a lens). These waves travel slowly and tend not to interfere with each other, which is why we see them superimposed in the picture. The density difference need not be as great as fresh/salt. The small difference between warm and cold water layers will support internal waves.
Internal waves can 'break' if they propagate into water shallow enough so that the level between layers intersects the bottom. This release of energy can suspend very fine sediment typical of the type produced by eroding of carbonate reefs (typical in Tahiti) which could be carried alongshore  andl cascade into deep water as indicated by the plume. However, afternoon sea breezes are a more likely driver for the sediment plume.