Pyura herdmani, one of two southern African species of "red bait" (or "rooiaas" in Afrikaans), is a sessile ascidian, or sea squirt, that lives in coastal waters attached to rocks or artificial structures.

[1] However, the tunic can be highly variable in terms of its morphology, which seems to depend largely on habitat type (which includes intertidal and subtidal areas, rocky and sandy substrata, sheltered and exposed sites).

[1] This species is found in coastal areas of the temperate, subtropical and tropical marine bioregions of southern Africa.

In the temperate provinces, its range overlaps with that of the morphologically similar P. stolonifera, a species that often occurs in sympatry and that can even hybridise with P. herdmani (M. Rius, unpubl.

Its confirmed northeastern distribution limit is Ponta do Ouro in southern Mozambique, but it is possible that it occurs beyond this site.