At first glance it may look like an oil spill but it’s actually a massive aggregation of anchovy near Scripps Pier at the Scripps Institution of Oceanography, UC San Diego in La Jolla, California. The gathering occurred on 8 July 2014 and the footage was taken by Scripps staff and underwater by Scripps graduate students Julia Fiedler, Sean Crosby and Bonnie Ludka.

It’s fascinating to see how the school reacts in unison to avoid the swimmers.