Dictyoceratid sponges do not have the usual mineral spicules (rod-like structures that make up many sponge skeletons). Instead they are made entirely of elastic spongin (protein) fibers organized into networks. This makes their bodies tough and flexible. They are easy to squish, but hard to tear. The surface of their body is typically raised up in little cone-shaped points, making it look like they have goosebumps. The bumps are actually projections from the underlying skeletal fibers, and in some species the bumps are expanded into an armor-like covering. Dictyoceratids have the habit of incorporating debris (such as sand grains or spicules shed by other sponges) into their skeletons, making them harder.

Because sponges cannot move quickly, they need ways to defend against predators other than fleeing. Some sponges have sharp skeleton parts (spicules) that protrude from their bodies and are also shed to make a spiny carpet around them. Chemical defenses are critical for sponges, too. Their bodies contain a range of chemicals that can make them bad-tasting or even poisonous to predators. Some of the chemicals are produced by microscopic organisms (such as bacteria and fungi) that colonize them. Both the sponge and the microbe get something out of such mutualism, with the sponge providing a home and nutrients for the microbe and the microbe working with the sponge to make defensive chemicals. Humans may benefit from this relationship as well, because many chemicals isolated from sponges have anti-cancer and anti-bacterial properties. Scientists are isolating specific chemicals from sponges to create life-saving drugs such as the anti-cancer Ara-C.