NASA’s Goddard Space Flight Center just shared these fascinating satellite photos taken in January 2014 over the shallow waters around Sisan Island, South Korea. The tiny patchwork of small squares are entire fields of seaweed that are held in place with ropes and buoys to keep the plants near the surface during high tide but off the seafloor in low tide. Via NASA Earth Observatory:

Since 1970, farmed seaweed production has increased by approximately 8 percent per year. Today, about 90 percent of all the seaweed that humans consume globally is farmed. That may be good for the environment. In comparison to other types of food production, seaweed farming has a light environmental footprint because it does not require fresh water or fertilizer.

They look like drawings; distinctly human marks.