During a maritime survey of the area offshore of Black Rocks, a pair of ship cannons were found, crossed over each other. The cannon both measure 242cm long, and approximately 100cm in diameter near the base ring. There is no evidence for a shipwreck in the surrounding area, and the area was not a historic anchorage due to the prevailing easterly currents. It appears that these cannon were intentionally discarded.

The cannons are located within the area of a proposed harbour development in Giles Quarter. Under the Malta Agreement, the developer (Rijkswaterstaat) will be required to ensure that they are responsibly mitigated ahead of development.