Obelia

n. genus of hydrozoan animals that form moss-like colonies on underwater structures (e.g. piers, ship hulls, etc.); female first name

Hydroid describes the polyp stage of a Hydrozoan lifecycle. Hydrozoans are a Cnidarian class that consists of mainly marine and some freshwater species, which may be solitary or colonial, and may have either a polyp or medusa lifecycle stage (and often both).
See more at Wikipedia.org...

n. Obelia, genus of hydrozoan animals that form moss-like colonies on underwater structures (e.g. piers, ship hulls, etc.); female first name

n. Obelia, female first name; genus of hydrozoan animals that form moss-like colonies on underwater structures (e.g. piers, ship hulls, etc.)