Most of the 5000 or more sponge species are marine, although some 150 species life in fresh water. Marine sponges are abundant in all seas and at all depths, and a few even exist in brackish water. Although their embryos are free swimming, adults are always attached, usually to rocks, shells, corals, or other submerged objects.
This orange demosponge, known as the orange icing sponge (Mycale laevis), often grows beneath platelike colonies of stony corals. The large oscula of the sponge are seen at the edges of the plates. Unlike someother sponges, Mycale does not burrow into the coral skeleton and may actually protect the coral from invasion by more destructive species.