The form of this sponge can be very polymorphic, varying from thin sheets, massive forms and cushions to branching-repent forms. Prone to give off stout branching processes which develop into oscular chimneys. The colour is also variable, green in well-lit sites owing to the presence of algae and cream-yellow in more shaded sites. The surface of the sponge is usually smooth, often with a slightly glassy appearance. This species can be difficult to identify in the field, however it does have a characteristic smell when fresh, once recognised this is a reliable character to use for field identification.