Maryland Code, Natural Resources § 8-728

(1) A lien given by statute or rule of law to a supplier of services or materials for the vessel;

(2) A lien given by statute to the United States, the State, or any political subdivision of the State;

(3) A security interest in a vessel during any period in which the vessel is inventory held for sale or lease by a person or leased by that person as lessor and that person is in the business of selling vessels;

(4) Any lien arising out of an attachment of a vessel;

(5) Any security interest claimed on proceeds, as defined in § 9-102(a)(65) of the Commercial Law Article, if the original security interest did not have to be noted on the certificate of title in order to be perfected; or

(6) Any vessel for which a certificate of title is not required under this subtitle.