Jellyfish kind of just float. In massive blooms. But there's actually some science to how they travel.  This image shows the pressure generated during the power stroke of a moon jellyfish, and it reveals that it creates a ring shaped vortex of spinning water.

The pocket of positive pressure pushes the body of the jellyfish to create extra thrust. And according to some calculations, the creation of the vortex makes them swim three times more efficiently than a salmon.

The most remarkable things are the simplest. [Proceedings of the National Academy of Sciences via New Scientist]