Search the indicated locations at the listed coordinates on the world map to find all nine 
hidden elite ship upgrade plans in special chests and get the "Destroyer" achievement:
1. Elite Round Shot: Kabah Ruins - 769, 145 coordinates
2. Elite Hull: San Ignacio - 379, 770 coordinates
3. Elite Swivel Guns: Devil's Eye Cave - 488, 353 coordinates
4. Elite Harpoon: Andreas Island - 579, 720 coordinates
5. Elite Broadside Cannons: The Blue Hole - 471, 170 coordinates
6. Elite Heavy Shot: Petite Cavern - 901, 263 coordinates
7. Elite Fire Barrels: San Juan - 479, 487 coordinates
8. Elite Fire Barrel Storage: Isla Providencia - 502, 44 coordinates
9. Elite Ram: La Concepcion Shipwreck - 181, 296 coordinates