Talk to the castaway "captain" in Pub Canach.
Bring a drink to the captain.
Listen to the rest of Captain Lakes's tale.
Find the diver.
Complete the Master Diver achievement, then return to Dive Master Astora.
Find the treasure in Sharkmaw Caverns.
Find the sunken treasure in the Siren's Reef fractal or Underwater Ruins fractal.
Look for treasure using your skimmer's Aetherlocation skill in Castora.
Defeat Taidha Covington to retrieve a piece of the mask from her reward chest.
Find the piece of the mask in the 'Booter's Path in Castora.
Find the piece of the mask in the base of Wiley's Buccaneers.
Discover where Wiley hid his piece of the mask.
Find the piece of the mask in Castora.
Find the mask piece on one of the freebooters in Castora.
Find the piece of the mask in Southsun Cove.
Find the piece of the mask in Lion's Arch.
Find the piece of the mask hidden in Orr.
Return to Captain Lakes to figure out how to put all the pieces together.
Speak to Cecil the Strong Arm.
Find the recluse from Weyandt's crew.
Find the Shark Spirit near the Honor of the Waves sanctuary.
Complete one of the explorable paths in Honor of the Waves to help the Shark Spirit.
Return to the Shark Spirit.
Return to the shaman.
Legendary Armor
