Coral polyps generally take up molecular oxygen that is dissolved in seawater directly by diffusion through their tissues. That O2 can move from the surrounding environment into the epidermal layers of the polyp or from the internal gastrovascular cavity into the gastrodermal (internal) tissues. Water-pumping cells within the gastrovascular cavity help the diffusion process here. Coral polyps create a network or colony with connective tissues (coenosarc) which connects individuals to others. The exchange for oxygen is constant through the surface of each polyp, but is shared through out the reef.