Rescuers Go Under

Location: Misery Falls (Grapple perk required)

Head to the marked location. The clue is found in front of a pickup truck wreckage, with a green flare. After starting the mission, look up to find the grappling points on the side of the cliff. Use it to reach the cave entrance at the top.

After reaching the cave entrance, you can either deal with the two bears in the immediate area or ignore them and jump to the flooded cave entrance. Dive towards the logs at the bottom then continue forth until you see the grappling points above the water in the end of the short tunnel.

Climb out of the water then pull yourself up and continue walking along the tunnel. Continue forth until you reach a large cavern with a waterfall. Attach to the grappling points and swing to the next ledge. From there, continue walking until the path collapses.

In the next area, swim towards the truck wreckage and skim through the narrow path to find an intact car lodged on a ledge, with a small container and note near it. Jump to that ledge so you can access the rear wheel of the car. Make sure to get close to it so you’ll get the prompt to release the brakes. Doing so will make the car slide and turn over, giving you a platform to reach the next ledge.

Climb that ledge and continue forth to reach the stash. Treasure hunt complete! After looting the goods, you just need to swim along the other tunnel to reach the waterfall. From there, you can just fast-travel, parachute, or glide down with your wingsuit.