The Envisat image shows a phytoplankton bloom swirls a figure-8 in the South Atlantic Ocean.
This image is fascinating because the phytoplankton act as natural tracer particles and reveal structures in the ocean such as the vortex dipole causing the figure-8. The phytoplankton reveal the velocity fields of the ocean currents showing where the flow is driven by shear vs vorticity.
Image Credits: European Space Agency (ESA), Envisat MERIS, December 2011
https://www.esa.int/Applications/Observing_the_Earth/FutureEO/Space_for_our_climate/Earth_from_Space_A_southern_summer_bloom
