From the introduction:
The world of the People is located in our planet, but it is probably the most alien environment a human being can imagine, where time and space loose their meaning entirely.
The People do not measure time. They live in eternal night, not divided by dusk or dawn, and their world does not follow the turning of seasons on the surface. Their environment has not changed since eons, even ice ages have not affected this unusual habitat, and today deep sea is much the same at the equator, and under the arctic ice cap. Their concept of time is therefore measured by their own lifecycle, or the lifecycle of other animals. They divide their life into stages: Larval stage, younger stage, reproductive stage and elder stage.
The People see space as something self-evident and omnipresent. Their world has few boundaries. The rocky bottom of the ocean is one of them, but as there are so few exciting places down there, they rarely visit the sea floor. The other one is the surface, but as their ultra-sensitive eyes can detect the smallest speck of light in the depths, even starlight makes them uneasy, and the low pressure causes them pain, if they would ever reach the surface, they would surely die.