They have to be as they can not make their own food as plants ( autotrophs ) can do. So, yes.
a hollow gut
It is called the Coelenteron or gastrovascular cavity.
importance of coelenterates
Yes, coelenterates are invertebrates.
harmful effects of coelenterates
A coelenterates habitat is in the ocean and if it is not it lives somewhere
Coelenterates are not cold nor warm blooded
Coelenterates that are found on Cornish shores include the sea anemones, true jellyfish and hydroids.
An animal derived from only two germ layers are called diploblastic animals. Eg: Poriferans, Coelenterates.
coelenterates
The term coelenterates is now out of date and has been replaced with two terms Cnidaria and Ctenophora. Animals covered by these terms are jellyfish sponges and coral like animals. So the water is where your most likely to find most of them.