Hi Walt,
You might have a bit of trouble picking up those small pieces with a stock PI, sort of VLF domain really. For pieces that small, you might be best trying a Bug, or GMT in a watertight housing, such as a Pelican.
Here in NZ during the goldrush days there were a lot of ships that foundered and broke up resulting in total loss of ship, cargo, and persons. They were usually trying to cross river bars in storms or when the river was swollen, to get those fever driven miners quickly onto new discoveries, and taking other risks that no Master in his right mind would normally take, if it were not for the goldrush rush.
Check it out, I'm sure Nome will have some too! They had the fever no doubt. A lot of those early miners were carrying a considerable amount of gold coinage (ironic really). So if the ship broke up on the shore you will discover all sorts of paraphernalia, fittings, personal belongings etc.
If you didn't need ground balance, and were only going down 2 metres at most, Eric's Aquasearch is a mighty powerful machine.
Cheers Kev.