Oceanography
There are 3 major disciplines of oceanograhy. One is marine geology & geophysics, phisical oceanography & marine chemistry & geochemistry. Oceanographers & others work together to solve mysteries & unknown of ocean science.
Marine Biology
They study marine organisms & their behaviors & interactions with the enviroment. Also to understand marine organisms & their behaviors marine biologist must understand of other aspects or "Disciplines" of oceangrahy, like chemical, physical & geological oceanography. In marine biology researcher picks a particular interest & specializ in it. Like particular species, organism, behavior, technique, or ecosystem.
Marine Mammal Biologist
Some peole have a masters or Ph.D but is not neccesary but people that study marine mammals hd B.S degree. Work time is about 8 hours per day in nthe ffice but in the field is about 12-15 hours per day. You can make about 40,000 & 80,000 USD er year.