HEllo,

Hope you are doing good.

Coming to your question, To join Merchant Navy you need to :

• The students have to complete 10+2 in physics, chemistry, maths with an aggregate of 50 percent of marks or equivalent to it from a recognised board.
• attempt popular entrance examinations  to become a merchant navy officer like: Indian Maritime University Common Entrance Test, Hindustan Institute of Maritime Training Online Entrance Test, Tolani Maritime Institute- Birla Institute of Technology and Science Entrance Examination
• opt for a bachelor’s degree programme in related specialization.
• Once the bachelor's degree is completed the student can either begin working in the field of merchant navy at an entry-level post or The candidate can go for his or her master’s degree programme in the specializations related to merchant navy.

For more details follow the below Link:

https://www.careers360.com/careers/merchant-navy

Good Luck