This habitable area is known as the photic zone.

这片适宜居住的地带被称为透光带。

In its current state, only certain parts of the oceans are considered to be in the photic zone.

在目前情况下，在海洋中，只有特定的一些区域是透光带。

But if the oceans were to be completely transparent, theoretically, every part of the sea would be a photic zone.

但如果海洋是完全透明的，那么就理论上而言，海洋的每一部分就都会是透光带。

The photic zone, which is bathed in sunlight during the day, and starlight and moonlight at night, reaches down a few hundred metres.

透光层白天沐浴在阳光之中，夜晚沐浴星光和月光，透光层低达几百米。