Summary Offences Act 1953

If a police officer in charge of a police station or holding a rank not lower than sergeant has reasonable cause to suspect—

that an offence has been, or is about to be, committed on board a vessel which is in any harbor, port, dock, river or creek; or

that a person who has committed an offence, or against whom a warrant has been issued by a justice, is on board a vessel, the officer may, at any time of the day or night, exercise all or any of the following powers:

the officer may stop and detain that vessel;

the officer may enter, at all times, with such constables as he or she thinks necessary, into and upon that vessel and every part of that vessel;

the officer may search and inspect that vessel and in doing so take all necessary measures for the effectual prevention or detection of any such suspected offence and for the apprehension of any such suspected person;

the officer may take into custody any person reasonably suspected of having committed an offence or liable to apprehension under paragraph (e);

the officer may take charge of all property suspected to be stolen or otherwise unlawfully obtained.