The most southern shore of Kings Canyon hosts a massive Water Treatment facility that is actually very similar to Swamps in terms of playstyle. Ziplining works here just as well, and if you like to loot in relatively empty locations, then this one is just perfect.
Many players don't land here in anticipation of finding good items, but actually Water Treatment always produces high tier loot and it's aplenty here.
Besides your typical loot that you will find on the ground, there is at least a dozen supply crates around the area. So this location should definitely be on your list.