13.—(1) Article 4 applies—
(a)to the deposit of any shellfish, trestle, raft, cage, pole, rope or line in the course of the propagation or cultivation of shellfish;
(b)to a removal activity or dredging activity carried on for the purpose of moving shellfish within the sea in the course of its propagation or cultivation.
(2) But article 4 does not apply—
(a)to any such deposit made for the purpose of disposal;
(b)to any such deposit made for the purpose of creating, altering or maintaining an artificial reef; or
(c)to any such deposit that causes or is likely to cause obstruction or danger to navigation.