There are many steps in the process to become a marine biologist, and many people start at a very young age, laying the groundwork for their college educations. The first and foremost step is an interest in marine life and the oceans, as being a marine biologist would not be very enjoyable if you weren't interested in your study subjects.
Marine biologists study ocean life, ranging from huge whales to tiny planktonic organisms. They have access to some of the most interesting places in the world, including hydrothermal vents, which host bizarre organisms that use chemosynthesis for energy. The ocean is a largely unexplored territory, which means that there is a lot of work to be done in marine biology, from monitoring the populations of commercial fisheries to studying global ocean temperatures and their effect on marine life.
If you want to get a job as a marine biologist, you should start as early as possible because there's a lot of math and science to absorb. In high school, taking classes in mathematics and sciences is a big help, and if you can access marine biology courses in your school or at a local college, you should definitely consider taking them. You might also want to see if you can intern with a marine biologist, or spend a summer working in a marine biology lab, to get a sense of the hands-on work required.
For college, if you want to become a marine biologist, you should select an institution with a marine science program, and preferably you should find a school which is affiliated with a research facility. This will give you an opportunity to get real field experience, and it will allow you to work in a wide variety of facets of marine biology to see what interests you most. After you graduate with a marine biology degree, you may be able to find work in the field, but you may want to pursue graduate work to become a marine biologist with better qualifications. Additional education will expand your depth of knowledge and make you more employable.
You may find that when you become a marine biologist, a particular aspect of the field interests you, such as microscopic organisms, marine mammals, marine habitats, coral reefs, or any number of topics. Many marine biologists figure out what they want to specialize in when they intern with experienced biologists in the field, getting an idea of what the day-to-day work is like. You may, for example, find that although you are fascinated by ocean life in deep sea trenches, you don't like having to work remotely to study organisms of interest. Or that you are drawn to education, zookeeping, or a variety of other careers in marine biology.
Marine biologists work as field and lab researchers, educators, and consultants. Oil companies, militaries, and fisheries all need marine biologists to monitor their operations and provide suggestions for increased efficiency and environmentally-friendly practices. Marine biologists also work with conservation organizations, wildlife advocacy groups, zoological parks, and national governments, among others, so there is a lot of room for employment in this field.