This falls under my interest in WWII tanks, and my tendency to make my gamers put their PCs into nasty, miserable marshes:
The Salvagers Who Raise World War Two Tanks From the Dead
How are the places they look?
"“It is easy to hunt when you are shown a definite point,” says Mikalutski. “But to get to the point you may have to go five kilometres through marshes or snow. You reach the place and then you have to crawl back...”
For the sake of their own safety, the tank hunters never go into the marshes alone."
Winter, it's been -33 C.
Summer? "“What a buzz it is at night. It seems mosquitoes will overturn the van.”
Insect repellents do not help in marshes. The conditions are extremely difficult in hot weather: they have to work in thick jackets and hats even when it is 30C because of clouds of insects."
And that's in a normal, Earth marsh. No monsters, no mutants, not even an enemy army. Add those and you get ADVENTURE!
For loot, note how well-preserved some of these things are - still-edible chocolate, untouched textbooks, etc. It's not unreasonable for PCs to have to unearth something from a nasty marsh in either the peak of summer or the depths of winter, dealing with natural hazards on top of whatever threats surround the long-buried and lost loot . . . it need not even be a tank. If you insist.