Giant tube worms, Riftia pachyptila, are marine invertebrates in the phylum Annelida (formerly grouped in phylum Pogonophora and Vestimentifera) related to tube worms commonly found in the intertidal and pelagic zones. Riftia pachyptila live over a mile deep, and up to several miles deep, on the floor of the Pacific Ocean near black smokers, and can tolerate extremely high hydrogen sulfide levels. These worms can reach a length of and their tubular bodies have a diameter of . Ambient temperature in their natural environment ranges from 2 to 30 degrees Celsius.