The oceans have a lot of potential for different kinds of living things, but only 16% of all known species are found there. The number of species decreases as you go deeper into the ocean. Scientists are trying to figure out how many marine species there are and how they are affected by things like deep-sea organisms and human activities. The species most at risk of disappearing are the big ones that only live in one place. To protect these species, we need to create large, fully protected marine reserves.