Animals that belong to the phylum Cnidaria exhibit specialized cells called cnidoblasts (cnidocytes). These cells play important roles in defence and capturing prey.
These animals are diploblastic having ectoderm and endoderm. They also show a tissue level of organization.
They possess a body cavity with only one opening.
All cnidarians are mostly aquatic animals. Examples are Actiniaria (sea anemone), Pennatula (sea pens), Physalia (Portuguese man o' war), etc.