First of all, it would be much darker the deeper you go. On the surface, the light from the sun touches the ocean, making the ocean look like a light blue. However, if you dive down even deeper, you will find a darker blue, and later nothing (the sun won't touch the deep parts of the ocean, so all you would see is darkness). The short answer to this is: It's lighter around the surface, and darker the deeper you dive down into the ocean.
Every organism is unique, even though the nucleotides making up DNA are all the same, because the structure is different in every organism. In other words, it's just the order in which nucleotides are placed that differs each organism from one another.
