6.—(1) The Commissioners may, if they think fit, require a person who incurs, or is about to incur, a charge to deposit with them, or to guarantee, such sum of money as is, in the opinion of the Commissioners, reasonable having regard to the amount or probable amount of the charge.
(2) Where such a person fails to deposit or guarantee the sum of money required the Commissioners may detain at the harbour the vessel or goods in respect of which the charge has been or will be incurred, until the requirement has been complied with or the charge has been paid.