What a person in this career does in detail:
A Marine Biologist studies from individual microorganisms to entire environments. They study Marine animals/fish and marine plants from all over the world. Some of the ways they study is to physically get in the water and swim with the animals/fish. They watch their behavior and their daily life, and study the many beautiful undiscovered plants. The animals they work with only live in saltwater areas, which could vary from dolphins to deep sea creatures or even tiny little plankton.
What branch of science most of this career falls under and why
life science, because it deals with real life animals and plants.