Sponges are animals with dense skeletons that are highly adapted to their environments, although it is easy to see why they may be mistaken for plants. Sponges are found in a wide variety of colors, shapes, and sizes – and scientists believe that the colors of the sponge may act as a protection from the sun’s harmful UV rays. Most sponges are found in the ocean, but there are certain sponge species that can be found in freshwater environments, as well.