79Professional staff off duty
(1)This section applies to a professional seaman in a ship at a time when—
(a)he is not on duty, but
(b)in the event of an emergency he would or might be required by the nature or terms of his engagement or employment to take action to protect the safety of passengers.
(2)A person to whom this section applies commits an offence if his ability to take the action mentioned in subsection (1)(b) is impaired because of drink or drugs.
(3)A person to whom this section applies commits an offence if the proportion of alcohol in his breath, blood or urine exceeds the prescribed limit.
(4)For the purposes of this section a seaman is professional if (and only if) he acts as seaman in the course of a business or employment.
(5)Where a person is charged with an offence under this section in respect of the effect of a drug on his ability to take action it is a defence for him to show that—
(a)he took the drug for a medicinal purpose on, and in accordance with, medical advice, or
(b)he took the drug for a medicinal purpose and had no reason to believe that it would impair his ability to take the action.