Marine Biology in general is basically a post graduation course and that is a very reason Google shows you MSc colleges only...

Yet there are some colleges like Setupathy Government arts college, Ramanathapuram which offers BSC under graduation course in Marine Biology field. Refer to the link below for knowing more about the same...

https://www.careers360.com/colleges/sethupathy-government-arts-college-ramanathapuram/bsc-marine-biology-course

You will need to complete your graduation course in BSC Biology any field and then you can choose Marine Biology as your post graduation course.

Some of the top universities offering MSC Marine Biology course are as follows -

1. Kerala University of Fisheries & Ocean Studies
2. Chettinad Academy of Research & Education
3. Andhra University
4. The Madras Christian College
5. The National Institute of Oceanography, Goa

Best wishes. Thank you.