Hello Rohit!
After doing MSc in marine microbiology there are a wide variety of career options which you can choose from. Definitely yes, marine microbiology is a good career option. After MSc you can get employment in various fields such as research, academics or company jobs. As a researcher you can get opportunities to explore the field of genetics, fossil microbiology, biochemistry, physiology, ecology, taxonomy etc., In academic field you can take jobs as lecturers, professors as a microbiology faculty. You can work with companies manufacturing marine food products or crude oil, microbial flora, petroleum products, etc., It depends on your choice and interest, what do you want to be. Hope this helps.
Good luck!