Barn... That makes me feel better that you kinda know what/who you're dealing with. Wow...you are determined! That guy didn't have two nickels to rub together.... and if he ever did I seriously doubt they were his.
I'm not encouraging this.. but it's the cheapest, inexpensive project I could think of and one that could be DEATHLY dangerous if not done right... but it works, IF done right. Not knowing the full layout of the land....all I can say is research a Cofferdam. You're still gonna need some equipment that you'd have to track to the location.
If you did happen to find a 3'x3' iron safe that was 20'+ down in marshland....The power needed to free it from the suction would be astronomical.
There's virtually no way to do a project like you've described without some equipment... And small crew. You shouldn't be out in marshland by yourself... I've stepped off in quicksand in Missouri and I went to my chest Fast. Luckily, I had taken one big step off solid ground not knowing it was quicksand covered in small flowers and it got me closer to a patch of solid grassy ground on the other side... I had a rifle with me and when I stepped off and went down, just instinctively I kept both arms up above me holding the rifle...or my hands would of been too slimy to hold on to that grass and pull myself out... minus boots and socks and covered in a slimy film.
Let us know how it goes.
Good Luck and Be Safe!
Kace
A Cofferdam, yes, sort of.
If I were ever to find a safe (with the four corners identified with yet more holes), then getting my relatives to help me would not be a problem anymore. (no comment)
We would hand dig a 5X5 foot shaft down and shore up the shaft sides as we go down with plywood (or something).
I know about ventalators from Home Depot to push fresh air in, and another one to pull bad air out.
I have a carbon monoxide monitor and other monitors to wear as we go down.
I already have a 3 inch gasoline powered trash pump with which to pump water out of the shaft as we dig down.
We would excavate the dirt, one bucket at time, using a rope and maybe a battery powered winch to bring dirt to the surface to dump it.
It doesn't matter how long it takes to dig the shaft, if it is known a safe really exists down there. (the problem is finding it...ha)
I would not even try to get the safe out.
I would open the safe while is was still down in the hole probably with a generator powered circular saw with metal cutter blades to cut it open...doesn't matter how many blades I would have to use...maybe the safe would even have hinges to make the work faster.
Then I would fill a bucket at a time with the loot, and use a rope to raise the bucket out of the hole...one bucket at a time until the safe was emptied.