Where do cnidarians live?

Cnidarians are primarily marine animals, though some species inhabit freshwater environments. They are found in a wide variety of aquatic settings, with their greatest abundance and diversity occurring in tropical waters.1

Their specific habitats depend on their body form:

• Polyps: Most require solid surfaces for attachment, though some burrow into soft sediments. While they are abundant in shallow waters, some, such as sea anemones, can be found in the deepest parts of the ocean.2
• Medusae: These organisms generally maintain a preferred depth in the water column and are transported by currents. Most hydromedusae and scyphomedusae live in surface waters, particularly in bays and along coasts, though certain species are also found in the open ocean.2

In tropical seas, the calcareous skeletons of many cnidarians form the structural framework for reefs and atolls.1