Far Cry 5 > Prepper Stash Locations and Walkthroughs
Stash Mission Start:
There is a note at the Salvage Camp.
Find the key to open the lockbox:
Time to dive. See the red buoy? There are a couple of those on the lake. Dive down to them. Best to follow the green flares underwater. The key is at the buoy that is furthest away (see map).
Key with dead body
Key location
Now you can open the box at the salvage camp. Money and 3 perk magazines.