The foam that you saw on Skaneateles Lake is naturally occuring. It is caused by a mix of decomposing organic material such as algae and air. When organic matter decomposes, it releases compounds. In the water, these compounds rise to the surface (surfactants) and reduce surface tension. Wind blowing across the lake disturbs these surfactants and creates bubbles. Wind patterns and water circulation cause these bubbles to collect in certain areas, creating the foam that you saw. The amount of foam that you see year to year is heavily dependent on temperature and amount of decomposed organic material, but again, nothing to worry about.
Foam can also be caused by pollution, but it would be pinkish in color and would smell like perfume. This foam is a nice bright white and shouldn’t smell like anything. You can touch it if you want, I’ve read that it is sticky like beaten egg whites.
The Skaneateles Lake Association noticed the foam as well and collected samples for analysis. If you would like to read more on that, follow this link.
https://skaneateleslake.org/lake-foam/