There are many good reports out there from people who live in Florida saying there is no mineralization to speak of in Florida sand. There have been inquiries made to Garrett regarding performance in salt water. Some direct quotes from Garrett and the AT Pro in saltwater include; "I would like to share with you some information provided by our engineering department.
First , is the AT Pro ideal for use in both fresh and saltwater ? Yes of course. However , your maximum performance will always be in fresh water.
Second , is the AT Pro equal in both saltwater and fresh water ? Not completely , no.
Third , will the AT Pro perform EQUALLY well at wet salt sand / water beaches detecting SMALL GOLD ? NO.
And fourth , if not , why not ? To condense the answer to this , it is because of the relative conductivity of saltwater and small gold ( they are almost identical ) . You have certain lines of defense to deal with saltwater when engineering a metal detector. Detectors respond to the relative conductivity of targets.( saltwater is conductive and looks like a thin foil to a detector ) You first have to design your coil , we made the DD coil , best for dealing with the highly mineralized salt water and mineralized soils with its narrow search field. It is a form of suppression. Next , there is Ground Balance . It is best described as adjusting a phase or phase shift. The goal is to be able to maintain a search field while basically overlooking or (ignoring ) the surrounding medium yet still finding the preferred targets. . (ie: ground minerals or in this case saltwater). Then you have discrimination. (ie; the pixel notch ) . This is necessary when you are looking for targets that are basically the same conductivity as your search field medium. You must deal with the conductivity of the salt water which is equal to your small gold. It is unlike searching for a needle in a haystack , yet more like searching for a needle in a stack of needles. No current VLF machine can do what you`re asking. Engineers are always creating and experimenting with new ideas. I hope this will help in your quest for answers.
A person can draw their own conclusions from this and many do, however, the part that strikes me is at saltwater beaches searching for small gold is like "searching for a needle in a stack of needles. No current VLF machine can do what you`re asking." Good luck and happy hunting.