By-the-Wind Sailor/Purple Sail/Little Sail (Velella velella)
Each Velella is a hydroid colony, and most are less than about 7 cm long. They are usually deep blue in colour, but their most obvious feature is a small stiff sail that catches the wind and propels them over the surface of the sea. Under certain wind conditions, they can become stranded on beaches in the thousands. Velella are carnivorous animals. They catch their prey, generally plankton, by means of cnidocyst (also called nematocyst) -laden tentacles that hang down in the water.
