The British fleet weighed anchor at Cape Fear on May 31 , and arrived outside Charleston Harbor the next day . Moultrie noticed a British scout boat apparently looking for possible landing points on nearby Long Island ( now known as the Isle of Palms ) , just a few hundred yards from Sullivan 's Island ; troops were consequently sent to occupy the northern end of Sullivan 's . By June 8 , most of the British fleet had crossed the bar and anchored in Five Fathom Hole , an anchorage between the bar and the harbor entrance . With the fort on Sullivan 's Island only half complete , Admiral Parker expressed confidence that his warships would easily breach its walls . Optimistically believing he would not even need Clinton 's land forces , he wrote to Clinton that after the fort 's guns were knocked out , he would " land seamen and marines ( which I have practiced for the purpose ) under the guns " and that they could " keep possession till you send as many troops as you think proper " .