Howzit 808beginnerdigger!
It sounds like you've got permission to work this lot, so you might as well dig a few holes
You know that there are bottles under there......somewhere
The problem is figuring out where the best place is to drop a test hole
You could try using surface clues - like the place where you found the Konishi shard, or you could do some probing
Now there are lots of different types of probes out there. Some are good for digging, others are good for probing.....
Check out this website for some killer probes:
www.tandttools.com
The TPA36 is a good combination probe. You can either dig or probe with it since it's only 3 feet long.
For deeper probing you may want to try the TPA48 (4 foot long) or the TPA72 (6 foot long).......
As for myself, I have all 3 of these, but for digging I use a TPA36-X7 (7/16" hex shaft) and the HH36S hook probe (1/2" diameter shaft).
These are super strong and can smash through the toughest iron layer in minutes!
In the picture below you can see them along with a "standard" hand-made probe (3/8" diameter shaft on far right). The TPA36-X7 is on the left and the HH36S is on the center right with the "hook" pointed up.