Offshore jobs usually refers to careers in the oil industry - I'm not sure if this is what you are looking for? If so, just put 'offshore jobs uk' in a search engine and you will find several lists of vacancies. For such jobs you may need experience in the oil industry or an engineering or technical background, but it's worth looking at the vacancies to see what is needed.

If you mean jobs connected with offshore banking, again an internet search for 'offshore banking jobs' is the best way to start. You may find offshore banking jobs uk especially helpful, but I would recommend exploring other sites as well. Requirements for such jobs vary a great deal, but generally you need a good standard in English and maths, preferably a foreign language and often a willingness to travel and possibly work abroad for long periods. There are also offshore jobs in the UK though, so this may not be the case.