The shark would be constructed with a built in metal detector
I think I know all metal detector types in commercial use and none of them would work in the ocean.
[...] and also simulate side to side movement like a real shark.
Does this concept seem to overboard or do you think it might be possible?
How old are you?
This sounds like something I'd ponder when I was ten years old - then I came to realize that most treasure hunts cost more than they net.
All to often we hear about Spanish ships that crashed off the coast to different US locations.
When somebody with years of experience and resources finds them, but they do't search randomly, they research a lot of sources for clues.
Well... Don't quit your day-job (if you're old enough to have one) to live on the loot
The fastest way to a quick buck is not spending it and getting a good education will help you earn it in the first place