Prepper's Stash: Swingers
The note for this stash can be found by some picnic tables, on the south end of a bridge east of the pumpkin farm.
Read the note to get started. As it says, you will need the grappling hook to complete the mission. Go ahead and purchase it if you haven't already- the stash at the end has three perk magazines.
There should be one sentry on the scaffolding under the bridge (if he hasn't been eaten by cougars). Take him out, then ascend to the top of the scaffolding yourself (you can risk a jump over, or jump down and climb the the ladders like a normal person would).
Once at the top, you'll notice a grapple point on the right edge of the bridge.
Grapple and swing out. You'll come within range of another grapple point. Tarzan over to it- you do NOT need to detach your current line first, just activate the new grapple point to switch over.
From that point, swing to platform under the middle of the bridge. You do need to detach here (unless you just slam torso-first into the ledge, in which case you'll automatically grab it).
Move forward. You'll have to jump a small gap to get to the next swing point.
You'll now do a three-point Tarzan, and again swing for a platform under the middle of the bridge.
Land there and explore this section. There are some minor lootables, but what you're looking for is the lightly colored platform with the medkit. Walk on it to trigger a colapse that will drop you into the stash proper.
Finding it completes the mission, but do remember to loot the place throughly- you'll find crafting supplies, money, medkits, knives, etc. You'll also find the compound bow, if you didn't grab the one on Dutch's Island.
Smash out the wall near the ashtray, and leap for the water when you're ready to depart.