Riftia pachyptila, commonly known as the giant tube worm and less commonly known as the giant beardworm, is a marine invertebrate in the phylum Annelida related to tube worms commonly found in the intertidal and pelagic zones. R. pachyptila lives on the floor of the Pacific Ocean near hydrothermal vents. The vents provide a natural ambient temperature in their environment ranging from 2 to 30 °C, and this organism can tolerate extremely high hydrogen sulfide levels. These worms can reach a length of 3 m, and their tubular bodies have a diameter of 4 cm (1.6 in).

Siboglinidae is a family of polychaete annelid worms whose members made up the former phyla Pogonophora and Vestimentifera. The family is composed of around 100 species of vermiform creatures which live in thin tubes buried in sediment (Pogonophora) or in tubes attached to hard substratum (Vestimentifera) at ocean depths ranging from 100 to 10,000 m. They can also be found in association with hydrothermal vents, methane seeps, sunken plant material, and whale carcasses.