As per the rules of UGC one can only pursue one full time degree course at a time. So you can't pursue BSc Microbiology and BSc Nautical Science at the same time. If you wish you can find out if there can be some colleges who offers the course in distance mode. Then you can go for any of the courses in distance mode and another in Full time mode. But remember keeping in track both the courses can be a problem.

To know more about Microbiology as career visit the link below:

https://www.careers360.com/courses/microbiology-course

To know more about Nautical Sciences as career visit the link below:

https://www.careers360.com/courses/nautical-science-course

I hope this answer helps. All the very best for your future endeavors!