Why does the ocean look so strange today?

The other day I flew out over the Pacific Ocean for a short distance, before the plane turned to the east and across the US. It was a sunny, calm day and the surface of the ocean sparkled. At the entrance to San Diego Bay, several calm slicks of water wound around, alternating with more rough-looking patches. I thought it might be interesting to look at some photos of various surface-ocean phenomena, and discuss why they occur.

This first phenomenon - slicks alternating with rougher patches of water - is essentially the surface expression of internal waves (with a nice calm surface). Internal waves occur underneath the ocean's surface where there is a density interface, such as at the thermocline. As surface and internal waves pass, the motion of individual water particles traces roughly circular patterns. The particle motions associated with crests and troughs move in opposite directions, and thus internal waves create vertical planes of compression and divergence. These are expressed on the surface as rough patches (compression) and slicks (divergence). Surface films that resist capillary motion also aid in the formation of slicks associated with internal waves.

Have you noticed that the ocean looks a funny color? It could be a plankton bloom: a population explosion of tiny organisms that live near the ocean surface. It may also be a runoff plume: sediment and/or nutrient-rich water flowing from land out to sea. Runoff can stimulate algae blooms, so it could be a combination of these - or you might just be noticing turbid (not clear) water arising from wave activity stirring up fine bottom sediments deposited previously in the coastal zone.

Does the ocean look as though someone spilled bubble bath? What you're viewing is seafoam, the formation of which is reminiscent of preparing a bubble bath. Vigorous agitation of the ocean surface by wind and waves, combined with high concentrations of organic matter from living or decaying organisms (proteins, sugars, fats, etc.) creates a froth of foam that can pile up on beaches. Algae blooms are a good source of organic matter that can then contribute to seafoam formation.

Now for one of the coolest ocean phenomena: bioluminescence! Many ocean animals emit their own light, created by a chemical reaction. Bioluminescence is a common feature of deep sea creatures that live below the photic zone, and is used for a variety of reasons. Some plankton also luminesce at night when agitated; when they have a population explosion (often called "red tide" because the plankton look red during daylight) the result is stunning - glowing waves, glowing fish, glowing dolphins, glowing swimmers. Anything that agitates the water creates a halo of blue-green light.

What other visual ocean phenomena have you noticed?

References:

Barger, W. R., Daniel, W. H., & Garrett, W. D. (1974). Surface chemical properties of banded sea slicks. Deep Sea Research and Oceanographic Abstracts 21(1): 83-89.

Craig, D., Ireland, R. J., & Bärlocher, F. (1989). Seasonal variation in the organic composition of seafoam. Journal of Experimental Marine Biology and Ecology, 130(1), 71-80.

Haddock, S. H., Moline, M. A., & Case, J. F. (2010). Bioluminescence in the sea. Marine Science, 2.

Monahan, E. C. (1971). Oceanic whitecaps. Journal of Physical Oceanography, 1(2), 139-144.