I tried it before, thinking I would go to the regular ocean beaches, for swimmer/fumble finger losses. And thinking that to be off-shore beyond he lowest tide points, is logically "virgin ground loaded with rings and goodies, woohoo". But the reality is far different:
You , as a scuba diver, know that the ocean bottom is not "constant". It has sand-dunes every-bit-as-much as the intertidal zone (more in fact). Barring unless you're diving on rocky surfaces? Anyhow, we soon discovered that there is no more coins/targets down there, than there is in the inter-tidal zone. Because JUST as the inter-tidal zone can have sterile sections, because the "sand was coming in", well SO TOO is the under-water zone susceptible to have zones of zero targets NO MATTER HOW MANY PEOPLE swam there the prior month or year or whatever.
I got a few coins and a silver earing on an all-day attempt. But I could've gotten 3x that if I'd simply worked the beach. Because under-water time is expensive and clumsy. Ocean current pushing you around while you fight like heck to 'stay on target'. And the minute you disturb the sand to dig a target, you get silt billowing up to cloud out visibility on what you're doing. Then you spend 5 minutes on your target, and FINALLY get it out of the sand at a foot deep: An aluminum can. Fresh as if it were lost yesterday (no corrosion whatsoever). So you know then, that a foot of sand came over where you are now trying, which is a disgusting feeling.
On the upper beach, that's no problem to "read" the beach, and simply go to low spots, which you can see 100 yards up or back on the beach. But you know underwater visibility simply isn't the same, to quickly put yourself on the likely low spots.
The video footage of the Mel Fisher type scuba, where it's cob after cob, etc... is not normal. They probably a) looked for months for that spot, and b) blasted away the sand with underwater fans, and c) that's shipwreck stuff where, go figure, thousands of targets are in an area the size of your living room. NOT the norm, and NOT regular beach fumble fingers losses type hunting. Hence that's just sort of like the bass-fishing channel, where "every cast is a lunker bass", and it "seems" easy, blah blah.
About the only place I could imagine scuba to be fruitful, is if you had a fresh-water lake (or perhaps bay-inlet on the ocean) where the under-water sand/bottom is not susceptible to currents . Hence the bottom is consistent and un-changing terrain. And where LOTS of swimmers, for MANY decades (like a swim lake with dive platform, etc...) existed. And would need to be a state/terrain where the water table is fairly constant. Not the "boom and bust" cycles of something like desert or chaparral terrain of the west. Where it goes dry every 10 yrs, , then washes out and silts in with new incoming water, blah blah (heck, you just wait for drought years, and walk out on dry land, doh!). So perhaps a reservoir where the water level is controlled is better.
I know that in some mid-west states, there are areas where the water level/table never fluctuates, historically, more than a few foot. Because the ground-water level is so shallow. Perhaps old picnic /swim/park lakes like that would be good for scuba md.
