Marine biologists generally require a 4 year undergrad BS degree in biology, then 2-3 years working towards a Masters degree. A Masters degree is sufficient to work as a Marine Biologist, though most Marine Biologists will pursue a PhD.
Make sure you take all the major sciences in high school, and make sure to do lab research during your undergrad, or you won’t have the necessary experience to get accepted into grad school, at least no here in the United States.
Some additional resources for you:
- Great article on the not so glamorous aspects of being a marine biologist.
- Colleges w/ the top marine biology programs in the U.S.