The endolithic and endopsammic habits in sponges promote similar morphologies and offer similar ecological niches of being protected and anchored. We assessed whether this also induces similar functions, i.e., whether the commonly endopsammic sponge Coelocarteria singaporensis (Carter, 1883) shares bioerosion capabilities with clionaid endopsammic sponges such as some Spheciospongia species, enabling it to inhabit and also to expand within calcareous substrates. We studied a range of traits that are commonly accepted as evidence for bioerosion. C. singaporensis has a globular or irregular body from which fistules arise, but the fistules never penetrated calcareous substrate, and while endopsammic specimens were able to agglutinate and incorporate particles, their bodies were not embedded within calcareous rock. Tough tissue filled small cavities in adjacent rock, but only in a few exceptions did we find sponge chips in it. We encountered the only indication for possible active bioerosion in the form of sponge scars and canals in some of the substrate the sponge touched or had embedded, but these areas lacked fresh erosion fissures and well-defined erosion scars and may have been made by other species. If C. singaporensis is able to bioerode, it does not seem to cut out chips to produce a regular shagreen pattern. The sponge clearly has the ability to insinuate into pre-existing cavities, but overall we regard the evidence for its bioerosion capability as circumstantial or unreliable. At this stage, we can neither confirm nor reject that this sponge may be able to bioerode calcareous material, but it appears to be unlikely.