The blue-colored swirl at the bottom right of this satellite image is an ocean eddy – a huge mass of water spinning in a whirlpool pattern. Eddies often spin off of major ocean current systems. The blue tint is a result of microscopic plant-like organisms called plankton, which grow as a result of the eddy stirring up nutrients from the deep to the surface. This image is from 26 December 2011 around 800 km (500 mi) south of South Africa. Image courtesy of NASA.