Spongia officinalis, better known as a variety of bath sponge, is a commercially used sea sponge. Individuals grow in large lobes with small openings and are formed by a mesh of primary and secondary fibers. It is light grey to black in color. It is found throughout the Mediterranean Sea up to 100 meters deep on rocky or sandy surfaces.

Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include greater than 90% of all species of sponges with nearly 8,800 species worldwide. They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite. They are predominantly leuconoid in structure. Their "skeletons" are made of spicules consisting of fibers of the protein spongin, the mineral silica, or both. Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges. Some species, in particular from the Antarctic, obtain the silica for spicule building from the ingestion of siliceous diatoms.