Basic seafarer requirements

Ok, first thing first, to become a seafarer, you are required to do the basic mandatory courses which include
fire fighting
personal survival at sea techniques
first aid
personal safety and social responsibilities
 Note that this has been made compulsory by IMO(international maritime organisation) and is subsequently being enforced by NIMASA here in Nigeria

 The course takes a week and no worries, you dont need a University or Polytechnic degree to run this course, you just need to have the passion to work on the sea.
Several maritime institutes in Nigeria already offer this certification but the most notable institutions are

• Maritime Academy of Nigeria, Oron, Akwa ibom State, http://www.maritimeacademyportal.org/#
• Charkin Maritime and Offshore Safety Centre Portharcourt 
• Coastal Maritime Academy, Ikoyi, Lagos, 08037008158

N.B. The fact that you are a graduate of Nautical science or Marine engineering does not exempt you from this course.All ratings, cadets, engineers, captains must have undergone or undergo this course.
After this course, you can proceed to do your seafarer medicals. The most popular hospital accredited by NIMASA for this purpose is the Nigerian railway corporation hospital, Oyingbo, Lagos.

Other accredited hospitals will be posted subsequently.

After you get your medical certificate, you will need your seamans discharge book. You can get this at 88 marine road Apapa, Lagos.
Remember to do your seafarer registration right after you get your discharge book. Its important too.
Then you are set, you can begin your seafarer career as a rating or a cadet.
You can visit this blog regularly for seafarer job vacancies.
Good luck!