The polyps are tiny and are supported by a hydrocaulus, a fairly stiff hollow tube with a perisarc (sheath) made of chitin and protein.

[2][3] Pennaria disticha probably originated in the western Atlantic Ocean but has spread and now is widely distributed in warm waters throughout the world.

[2] The polyps of Pennaria disticha spread out their tentacles to catch any small zooplankton that float by.

After drifting with the plankton for some time, this finds a suitable hard surface on which to settle and start a new colony.

[2] It has been reported that an acute, painful dermatitis occurred in several people who came into contact with a rope on which Pennaria disticha was growing as a fouling organism.