(1) The subject-matter insured must be designated in a marine policy with reasonable certainty.
     (2) The nature and extent of the interest of the assured in the subject-matter insured need not be specified in the policy.
     (3) Where the policy designates the subject-matter insured in general terms, it shall be construed to apply to the interest intended by the assured to be covered.
     (4) In the application of this section regard shall be had to any usage regulating the designation of the subject-matter insured.