Hello aspirant,

To become a 3rd officer in Merchant Navy, you must have Physics, Chemistry, Mathematics and English as separate subjects in your class 12 with average marks not less than 60%. Then you can do Diploma in Nautical Science and then BSc in Nautical Science. After completing the college you can go to sea as a cadet and complete the training then sit for exams, give interview and get the 2nd mate license and sail as a 3rd officer.

Hope this helps,

All the best!!