Protodermis Sea

The Protodermis Sea was the seemingly endless ocean that Metru Nui floats in the middle of. The Toa Metru crossed it when saving the Matoran from Makuta. During Makuta's battle with Toa Vakama the Vahi Kanohi Mask of Time was knocked into this sea. It was crossed again when the Toa Metru were returning for the rest of the Matoran. It was later crossed by the Toa Nuva when they were returning to Metru Nui in their quest to awaken Mata Nui. The sea was the equivalent of Blood for Mata Nui's body.