(a) Prohibition.—A common carrier by water may not, directly or indirectly, through an agreement, conference, association, understanding, or otherwise, prevent or attempt to prevent any other common carrier by water from serving any port described in subsection (b) at the same rates the first carrier charges at the nearest port already regularly served by it.

(b) Ports.—A port referred to in subsection (a) is one that is—

(1) designed for the accommodation of ocean-going vessels;

(2) located on an improvement project authorized by law or by a Federal agency; and

(3) located within the continental limits of the United States.

(c) Other Authority Not Limited.—This section does not limit the authority otherwise vested in the Secretary of Transportation and the Federal Maritime Commission.