If commerce student become marine biologist

   

A commerce student cannot be a Marine Biologist and must be a  science subject in class 12th for example Physics, chemistry and biology, math with minimum 55%

 In bharat, the marine biology course at UG level is BSc in Marine biology. This is a three year long course. The basic eligibility for this course is that you must have qualified class 12th with subjects Physics, chemistry and biology. And a minimum score of 55% must be obtained.
The admission to the course is generally based on the merit score of class 12th exam but some universities might conduct their own entrance exam
After the UG course, you need to go for PG course MSc in Marine Biology. It is a 2 year long course and gives indept study about marine science. The eligibility to apply to this course is a bachelors degree with minimum 50% aggregate marks.
The admission is based on university level entrance exams.
After Your MSc, you can pursue higher studies like MPhil in Marine Biology and PhD in Marine Biology.