No,
You cannot just give the science exam to join the Merchant Navy. Most merchant navy academies require a 10+2 qualification with Physics, Chemistry, and Mathematics (PCM) as compulsory subjects. To join the Merchant Navy, you typically need to clear entrance exams like IMU CET, which test your knowledge in PCM. After clearing the entrance exam, you will need to pursue specialized courses like B.Sc. Nautical Science or B.Tech Marine Engineering.

While your BCom degree is valuable, it doesn't fulfill the academic requirements for the Merchant Navy.

I hope this information helps you.