Salp

A salp is a barrel-shaped, planktic tunicate. 
Salps moves by contracting. This pumps water through their gelatinous bodies. It is one of the most efficient examples of jet propulsion in the animal kingdom. 
The salp pumps water through its internal feeding filters and feeds on phytoplankton.
Salps are common in all seas. The most salps are in the Southern Ocean (near Antarctica), where they may form enormous swarms, often in deep water. They are sometimes even more abundant than krill.
Although salps look similar to jellyfish with their simple body form and behaviour, in fact they are chordates. This means they are animals with a dorsal nerve cord. They are related to vertebrates, animals with backbones.