Understandably, the ocean floor receives very little sunlight, because of how far down it is and the way that water molecules scatter and absorb light. As a result, the organisms have many adaptations to help them survive even this harsh climate.
Similarly to the ocean floor, the bottom of a rain forest doesn't receive much sunlight either. The plants there have adapted to have huge leaves, so that they can get as much sunlight for photosynthesis as possible.