The master of a vessel who fails to comply with a general or special direction shall be liable to a fine not exceeding two hundred pounds.

It shall be a defence to the master of a vessel charged with an offence under subsection (1) of this section to prove that he had reasonable ground for supposing that compliance with the direction in question would be likely to imperil his vessel or any person for whom he is responsible or that in the circumstances compliance was impracticable.