I am not all that familiar with the exact job opportunities in India, but I would assume there are jobs available. Anywhere around the world where there is an ocean/sea has job opportunities in marine biology. A lot of the jobs will be connected with the government or with universities/higher education, but the opportunities are there. There should definitely be opportunities for research or conservation projects going on, especially with the diversity of the Indian Ocean. I would recommend doing some more research to figure out exactly what you want to do with marine biology, then reach out to government agencies or universities to figure out exactly what work they are doing in India.
From what I know, there are two major institutions that I have heard that are working in marine sciences in India: Satyabhama Institute (Tamil Nadu) and another in Goa. You can contact them for lab opportunities as an intern though I am not sure about the job application procedures.
There are several jobs available for marine Biologists, specially government jobs. the application for marine biology is in the field of aqua culture, shipping, marine engineering, etc. It is an exciting field even you are not looking only at the biology part of it, Marine biology is important in terms of research and development of surface finishing materials for ship design, naval architecture, etc.