the sessile, polypoid stage of Hydrozoans.

Small invertebrates whose colonies can take many growth forms including flower-like, tree-like or feathery. Hydroids are best represented in cool temperate southern Australian seas.

Marine organisms within the phylum Cnidaria that have life cycles in which they alternate between a plant-like, polyp stage and a medusa stage. During their polyp phase, individual hydroids tend to come together to form colonies. These colonies are commonly seen in bottom photographs from Georges Bank.

Animals of the taxonomic group Hydrozoa, a class of cnidarians that are made up of colonies of polyps. Hydroids often look like small ferns.