Sponges are from the phylum Porifera. They are some of the most simple animals in the ocean. They are huge colonies of cells without a central nervous system. They are really a huge group of individual cells built into a colorful and intricate structure. Sponges come in many different shapes and sizes, and they add splashes of color to a coral reef.
Sponges are full of holes and very porous. This is to allow water to pass through them. They are filter feeders, meaning they pull tiny plankton out of the water and eat the microscopic bits of food that flow in the current. They have tiny hairs that wave in the water, pushing water past them and allowing them to grab bits of passing food. They serve to help keep the water clean.
The household sponges we use today were designed after sea sponges. There used to be a major industry for harvesting sea sponges for use in household cleaning. Because of its destructive effects on the marine habitat, this practice has been replaced by more environmentally friendly synthetic sponges.