(1)If the skipper of or a seaman employed or engaged in a United Kingdom fishing vessel is, while on board the vessel, under the influence of drink or a drug to such an extent that his capacity to fulfil his responsibility for the vessel or, as the case may be, carry out the duties of his employment or engagement is impaired, he shall (subject to subsection (2) below) be liable-
(a)on summary conviction, to a fine not exceeding the statutory maximum;
(b)on conviction on indictment, to imprisonment for a term not exceeding two years or a fine or both.
(2)In proceedings for an offence under this section it shall be a defence to prove that at the time of the act or omission alleged against the accused he was under the influence of a drug taken by him for medical purposes and either that he took it on medical advice and complied with any directions given as part of that advice or that he had no reason to believe that the drug might have the influence it had.