WHERE IT STARTS:
The Treasure Hunt starts at the East Coast of BARRIAL - The CALAVERA CAVE, east of the OKU CREEK CHECKPOINT.
It's at water level.
THE NOTE SAYS:
"ATTRACTION CLOSED - DO NOT ENTER
Tourism operator license for Calavera Cave has been revoked for the following violations:
-Dangerous historical contraband sold in the Gift Shop, leading to:
-Multiple and catastrophic on-site fatalities.
Trespassers will be prosecuted!
May 7th, 2009"
WHAT TO DO:
Written guide below the Walkthrough Video
Smash the entrance to the cave and go inside. You have to complete the whole tour to get to the chest.
Follow the staircase up and use the grapple on the ceiling where it's broken to swing on the higher platform.
Continue the path and follow the ship's wheels back into a cave higher up. Here's you have to smash another barricade to get inside.
Make your way through the cave by just jumping - no grappling here - until you get to the ship.
The greenish-yellow glow in the water of the ship looks suspicious but it's where you have to dive through to the other side.
Don't miss the Hidden Histories document here. A skeleton is holding a book at the other end of the dive.
Climb up onto the deck and use the cannon.
All you need to do now is use the grapple on the ceiling to climb back up and get to the chest.