Where are the best institutes in the world for marine engineering? I am thinking about doing structural analysis etc. on ships and offshore structures.
We don't know from where you are and which countries will accept you. Developing countries usually have an ample supply of loafers and passengers but always needs trained technical people.
My advice is to stop thinking and start doing something in your own country. If you are good at it you may apply or get invited to other places.
If you intend to study you have to enquire at different places about the courses (standards & content) and admission requirements until you find something suitable for you.
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Never do today what you can put of until tomorrow - Student motto
You could try AMC (Australian Maritime College) Launceston Tasmania. They have a very good reputation and several big ships to practice on!
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"A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools!" Douglas Adams 1952-2001. E&OE!