The North Sea is cold and windy, and seemingly rather inhospitable. But for phytoplankton, it can be paradise.
These microscopic organisms are the basis of the marine food chain. They take energy from sunlight and use it to make sugars to power themselves. Other tiny creatures then eat them, and get eaten in turn by bigger animals like fish.
When conditions are ideal they form huge green blooms that can be many kilometres across.
This image shows them at their peak in the North Sea. It was captured on 11 June 2015 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite.
The United Kingdom is on the left, predictably under a lot of cloud, with Norway top-right and Denmark bottom-right.