The Plenty is a term used by the sea serpents. The world beneath the border of the Lack, or below the sea's surface, is the Plenty. It provides everything the sea serpents need or want: food, resting places, tides and the company of their tangles. There's nothing for them in the Lack, because they do not yet know that in truth they are the Lords of the Three Realms. They only briefly visit the Lack at nighttime to sing together.