Around noon the frigates Sphinx , Syren , and Actaeon were sent on a roundabout route , avoiding some shoals , to take a position from which they could enfilade the fort 's main firing platform and also cover one of the main escape routes from the fort . However , all three ships grounded on an uncharted sandbar , and the riggings of Actaeon and Sphinx became entangled in the process . The British managed to refloat Sphinx and Syren , but Acteon remained grounded , having moved too far onto the submerged sandbar . Consequently , none of these ships reached its intended position , a piece of good fortune not lost on Colonel Moultrie : " Had these three ships effected their purpose , they would have enfiladed us in such a manner , as to have driven us from our guns . "