Crinoids are the oldest surviving echinoderm lineage, and most fossil forms were permanently attached by a stalk. Feather stars, the comatulids, keep a stalk only as larvae. The adult holds on with cirri and can release, then row through the water by lifting arms in alternating groups so that some push down while others recover.
The swimming is slow and short-range, typically a matter of seconds to a minute, and appears to serve escape and repositioning rather than travel. Feeding is done stationary: the arms bear side branches called pinnules with tube feet that catch plankton and pass it along ciliated grooves to the mouth, which faces upward rather than down.
Crinoids are often called sea lilies indiscriminately, but that name properly belongs to the stalked forms. Feather stars are also frequently taken for plants or soft corals in photographs. Their arm counts vary widely between species, and the developmental control of arm number in the group is still an open topic.