Here's why:

* Photic Zone: This is the uppermost layer of the ocean where sunlight can penetrate. Sunlight is essential for photosynthesis, the process by which algae create their own food.

* Aphotic Zone: This zone lies below the photic zone, where sunlight cannot reach. Without sunlight, photosynthesis is impossible, and therefore, algae cannot survive there.

Exceptions:

While most algae need sunlight to survive, there are some exceptions:

* Chemosynthetic Algae: Some types of algae live in environments like hydrothermal vents, where they utilize chemical energy instead of sunlight for their energy source. These are not dependent on the photic zone.

* Deep-sea Algae: Some algae may live in the upper part of the aphotic zone, taking advantage of the very faint light that penetrates. These are still limited in their distribution compared to algae in the photic zone.

In summary, the vast majority of algae need sunlight for photosynthesis and are found in the photic zone.