Why does the light reflecting off of ocean water sometimes appear 'smoother'? Looking out the window at some water in the Harbour - I noticed that some parts of the water appear 'smoother' than others. 

My question is: Why does the light reflecting off of ocean water sometimes appear 'smoother'?
 A: I've also seen this, and wondered what it is! I thought they may have been some sort of surface currents as they looked like "rivers" to me. However, I've just done some searching and found this and this. So the answer is biogenic slicks, oily substances exuded by algae washed off from the shore! These don't dissolve well with water and form a thin film over it (apparently only about one molecule thick!), which has a higher reflectivity.
This higher reflectivity probably gives the illusion of being 'smoother', as for the same reflectivity, a smoother surface would reflect more light (under diffuse illumination). I assume this is the reason as a one-molecule thick film probably won't change the actual surface roughness. This agrees with my observation that when light isn't reflecting off these places I can't see any difference at all. EDIT: Here it says that the monomolecular films do actually cause dampening of short gravity waves. It seems this is due to a so-called Marongini effect, which has been studied, and looks quite interesting.
From reading this, I think that currents actually do play a role in this effect. In particular, in the actual formation of the accumulation of algae and thus of their oily exudates. This may explain why I have seen them mainly when flying off the airport off Gibraltar where there are strong tidal currents flowing out of the Mediterraneans.
In here, it explains why the thin film is so thin for the biological slicks, compared to the mineral oil ones. The reason is that the biological compound has a hydrophilic and a hydrophobic part, like soap, and this spontaneously forms a very thin film with the hydrophilic part towards the water. Here gives some references to details of the compositions of these slicks. It says it's mainly proteins, lipids, organic acids, saccharides and metals.
Other sources, apart from oil spills, also seem to be fishbait from fishing activity.
A: Two potential reasons among others: the wind is not uniform, if it blows larger on one sector it will move the water surface stronger. Second, different smal surface waves that come from different directions can interfere either negatively or positively, depending on their relative phases, over some small region, which again wouls result in inhomoheneities in the observed disturbances 
A: Most likely what you are seeing is a thin film of oil floating on the surface of the water that comes either from natural underwater sources, runoff from the shore, or from ships. The oil breaks the surface tension of the water and reduces traction forces from the wind - thus ripple amplitudes are reduced or entirely diminished.
This phenomena has been known for years going back to at least early greek civilization who learned to quell the surface of the sea by throwing (I suppose olive) oil overboard.
