Our Sullivan's Island is located in the Cannon River behind the center field scoreboard of the Dukes of Dundas's ballpark. That's where the listed coordinates will take you. The original Sullivan's Island in South Carolina was the setting for Edgar Allen Poe's "The Gold-Bug", as well as the place where he wrote the short story. But it's part of the Charleston sprawl so the one in Dundas is more appropriate now.
The hero in the tale, LeGrand, finds a map and encoded message for a treasure hidden by Captain Kidd. To read more about the story, and especially to be able to crack the code, refer to a copy of "The Gold-Bug" such as the one at Gold-Bug
Please note that not all letters of the alphabet are included, especially a few that occur infrequently. For those we'll let them stand for themselves. In particular, W remains W and K remains K. Similarly, due to printing restrictions, some deprecated symbols in the coded text have had to be replaced. Thus, the dagger has been replaced by an exclamation point (!) and the double-dagger by a plus (+). Otherwise the code is the same as in most copies of the story.
The listed coordinates will take you behind the scoreboard. Then proceed west to the edge of the river. There you'll find the devil's seat. You'll know you're there because there's a bug in a hole. The encoded message below will take you from the devil's seat to the death's head and hence to the treasure.
1 5 - 8 ) ) W 5 - ( + ) ) ; 4 8 W 5 ; 8 ( * + ; 8 ; W + 0 5 ( 3 8 9 ? 0 ; 6 ; ( ? * K 8 ! ; ( 8 8 ) W 6 ; 4 5 1 5 0 0 8 * + * 8 6 * 2 8 ; W 8 8 * ; 4 8 ! 8 5 ; 4 ) 4 8 5 ! 6 ) 6 * ; 4 8 9 6 ! ! 0 8 + 1 ; 4 8 ; + . 0 6 9 2 + 1 ; 4 8 1 5 0 0 8 * ; ( 8 8 3 + ; 4 8 ( 8 1 ( + 9 ; 4 8 ! 8 5 ; 4 ) 4 8 5 ! 3 + ;+ ; 4 8 2 5 ) 8 + 1 ; 4 8 9 ? 0 ; 6 ; ( ? * K 8 ! ; ( 8 8 ;+ ; 4 8 * + ( ; 4.
There you will find the treasure in the base of a tree in a small container.
This cache should not be attempted where the river is high or fast!