People of the Water
The People of the Water were a race of people. They once lived in, or possibly just near the ocean.
They made the Sea Temple and the Sea Crown. They are apparently extinct, and Lizabeth, Shep, and Lizabeth's parents are all descendents of them.
They also possessed surprisingly advanced technology or mechanisims that are activated by special crystals, which when activated are capable of preforming a multitude of tasks, from opening doors to keeping the sea temple from sinking.