No person shall set any post, drive any spile, or erect or continue any obstruction into or upon the public waters adjoining to and on the westerly side of Goat Island in the harbor of Newport, between the island and the main channel which separates the island from the island of Conanicut, or interfere with or injure any wire, torpedo, or other implement or contrivance in the waters, placed there under the authority of the United States, for use in connection with the experiments in torpedo practice carried on from Goat Island; but nothing herein contained shall be so construed as to give to the United States jurisdiction over any of the public waters to an extent which they do not already have, and this section may be modified or repealed at the pleasure of the general assembly. Every person violating any provision of this section shall be fined one hundred dollars ($100).