The amount:
(a) that the owner of a ship is liable, or the owners of 2 or more ships are jointly and severally liable, under the applied provisions of the Convention, to pay to the Commonwealth by way of compensation for any expense or other liabilities incurred by the Authority in, or by reason of, the exercise of the Authority's powers under section 8, 9 or 10 of the Protection of the Sea (Powers of Intervention) Act 1981 ; or
(b) that the owner of a ship is liable, or the owners of 2 or more ships are jointly and severally liable, to pay to the Commonwealth under section 20;
is a charge on that ship, or on each of those ships, as the case may be.