Sponges filter food particles out of the water by forcing the water through their porous bodies with a self-generated miniature current, which brings particles within reach of the walls of their pores where cells absorb them. Sponges are complex organisms whose cells perform many different tasks such as directing the flow of water through the sponge, extracting nutrients from food and many other things.
The muscular actors which filter water through a sponge's pores are called flagellae. They beat water into a consistent current which then draws in a steady stream of nutrient-rich seawater for the sponge to filter and feed off. These streams of water can even run counter to the ambient current in the surrounding waters of the ocean.
Sponges are communal organisms which consist of colonies of cells. The cells working in combination make the sponge a viable organism which can feed and reproduce, but the cells are also notable for being far more independent from one another than the cells of a typical animal.
A very few species of sponge exhibit carnivorous behavior, eating some crustaceans and other sea life whole. They accomplish this because their prey adheres to them thanks to their rough, hooked surfaces which latch onto crustacean shells and other prey.