Image from Guia Marina

Sponges are memebers of the Kingdom Animalia and Phylum Porifera which is split into three classes Class Calcarea, Class Demospongiae, and Class Hexactinellida.
Class Calcarea is a sponge found only in marine environments. They have spicules composed of calcium carbonate and relatively simple shapes.

Image from Coral Reef Divers

Image from NSUC

Class Demospongiae are usually very colorful and very common.

Class Hexactinellida is not a very diverse group of sponges. They can be found at depths of up to 3000 meters and can live for up to 9000 years.

Image from BioMedia Associates