There are more than 10000 species, mostly are marines and are invertebrates (are not corals !) Sponges do not have nervous, digestive or circulatory systems.
They are filter feeders that suck the surrounding water through small holes to obtain food and oxygen, they expell through a larger number of holes the wastes.
Reef sponges vary in color, size and shape, the shapes of their bodies are adapted to maximize the efficiency of the water flow. Sponges can be divided into two groups: Glass Sponges and Flat Sponges, all of them are found covering non–living surfaces.