(e) make provision for ascertaining and testing the standards of competence of masters and of any other members of the crews of vessels the subject of licences, whether by examination, interview or otherwise, and the prohibition of those who do not reach such standards of competence as the Minister considers appropriate from working as masters or, as the case may be, other members of the crews of such vessels and the prohibition of owners of such vessels from employing as captains or other members of the crews of the vessels those who do not reach such standards as aforesaid,