Hello Yoder,

Welcome to our scuba fourms!

You are right, the story does sound far fetched, but so do most stories of lost treasure. The thing is sometimes no matter how strange they sound, they are true. I am sure you will find something in your search, maybe not the treasure you were looking for, but something.

Anyway a magnetometer will most likely not work for you, as it is going to be looking for larger metal objects like a shipwreck. I am not 100% sure though as the technology changes quickly. Most likely you will need to use an U/W metal detector. There are many brands and models out there, and are designed for different uses. There are also different heads available for different uses as well. Obviously you want something that is designed for fresh water and that can penetrate deep into the mud. There are larger tow behind metal detectors as well, but they are going to be very expensive.

As far as searching and making a grid, fishermen and such:

You can still make a grid on paper and drop bouys to mark your locations. I would say a good GPS can help you keep things in order.

Good luck, have fun, and let us know how it goes.