Jellyfish
Jellyfish have no specialized circulatory system. Oxygen is easily absorbed through their thin bodies. Food is absorbed through the gastrodermis, which lines the gastrovascular cavity. The gastrodermis then passes the absorbed nutrients through the mesoglea then into the epidermis.
Coral
Coral has a gastrovascular system. This means the digestive and circulatory system(s) are somewhat jumbled up inside the body. Food is taken into a central gastrovascular cavity, often with branches into the tentacles, where digestions is extracelluar followed by intracellular digestion. The branches of the gastrovascular cavity allow food particles to travel to remote parts of the body and therefore serve a rudimentary circulatory system function. No true circulatory system
Sea Anemones
Sea Anemones have no true circulatory system. Their stomachs serve as there "circulatory system" because it’s a gastrovascular system. They also are given better circulation through the many species of fish that live symbiotically with the coral and sea anemone. Almost the same as coral except that Sea Anemones can move.