GW2 Sky Pirate Cache Achievement can be obtain by completing several jumping puzzles through Tyria, and approaching Aetherblade Caches at their end, mid or starting point. Aetherblade Caches are easily noticeable at the minimap and global map as event star icons.
There are seven Cache achievements and their names are the following:
Location: Fireheart Rise, Vexa’s Lab Jumping Puzzle.
Vexing Aetherblade Cache can be found just before the last room inside the Vexa’s Lab Jumping Puzzle.
Location: Caledon Forest, Tears of Itlaocol Jumping Puzzle.
Weeping Aetherblade Cache is in the last room of the jumping puzzle.
Location: Timberline Falls, Sector Zuhl.
Troll Aetherblade Cache is inside the Sector Zuhl area, near the entrance to Only Zuhl jumping puzzle.
Location: Metrica Province, Goemm’s Lab Jumping Puzzle.
Mad Aetherblade Cache is at the end of the jumping puzzle.
Mount Maelstrom, Hidden Garden Jumping Puzzle.
Cantle Aetherblade Cache is on the ground level of Hidden Garden jumping puzzle, and there is no need to reach the end of it, in order to acquire the Cantle Cache achievement. Mysterious Portal that takes you to Hidden Garden Jumping Puzzle appears after defeating one of four creatures named Keepers of Winds.
Harathi Hinterlands, Fawcett’s Bounty Jumping Puzle.
Shipshape Aetherblade Cache is inside the last cave of this puzzle, at its very end.
Eternal Battlegrounds (WvW map), Obsidian Sanctum Jumping Puzzle.
Blackout Aetherblade Cache can be found near the Obsidian Sanctum Chest, at the very end of Obsidian Sanctum jumping puzzle. In this case your home server needs to hold one of three Keeps at Eternal Battlegrounds, in order to have access to Obsidian Sanctum Jumping Puzzle.