Hello, Hope you are doing well, here is the answer to your question, To be frank drawing is needed but not compulsory in merchant navy nautical science because you do have Chartwork, Naval Architecture, Sea Structure etc in your course where you should know a little bit of drawing. Even if you are able to draw the rough sketch of it, it is well and good. Once if you are really interested in merchant navy stream even if you don't know drawing it doesn't matter much, the interest in the subject will drive you off.

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Wish you good luck!:)