The patch is characterized by exceptionally high relative concentrations of pelagic plastics, chemical sludge and other debris that have been trapped by the currents of the North Pacific Gyre.[2] Because of its large area, it is of very low density (4 particles per cubic meter), and therefore not visible from satellite photography, nor even necessarily to casual boaters or divers in the area. It consists primarily of a small increase in suspended, often microscopic, particles in the upper water column.