Sponges (Porifera) are among the simplest animals, but that hasn't stopped them achieving remarkable diversity. With hundreds of millions of years to hone their talents, they've gotten very good indeed at what they do.
The Blue World video below starts with a three minutes on the history of sponge collection and human use, followed by an introduction to their biology. However, it is at the 5:40 mark that it covers territory that's really impressive. Jonathan Bird adds a non-toxic dye to the water around the base of some sponges and the result is almost hypnotic in its beauty.
As one of the most ancient animal phylum, lacking tissues, organs and body symmetry sponges teach us a lot about where we came from, as well as what can be achieved with incredibly simple architecture.
Although most filter feed in the way Bird describes some deep sea sponges manage to tackle crustaceans.
As a predominantly marine species, we've barely scratched the surface of sponge diversity – carnivorous behavior wasn't observed until the 1990s. The ping pong tree sponge has been found at depths of 3km in the Mariana Trench, suggesting there could be plenty more we don't know about at depths we seldom reach. Lacking the capacity to move around or fight predators off, sponges have needed to come up with other forms of protection. Simply not being all that nutritious is not enough. The chemical defenses they've been working on for millions of years may have potential uses for us, for example as an inhibitor of cancer.