When hunting the dry stuff you want to find a beach that is cut, otherwise you should hunt the towel line. By cut I mean a distinct drop off running parallel to the waterline where the waves and tide have stripped away a layer of sand to form two distinct levels in the beach, the bigger the drop the better.
What you are trying to do is extend the range of your detector by working areas of beach that are newly exposed ie. before the sand was stripped away to the new level you would have had to penetrate that depth of sand before you even reached the new level after the waves/tide stripped away the sand. The sand having been stripped away now allows you to search areas of the beach depth-wise that would have been out of the detecting range of your machine prior to the stripping away. Essentially you now have a new beach to hunt with access to better targets as the gold tends to sink deep because of its density, but search it right away as the next tide will allow the gold to start settling deeper and out of your detector's range.
Always check the 3 feet of beach back from the cut as this area will actually have coins thrown up onto it by wave action, weird but true.
Searching sand dunes that have been created by wind action is largely a waste of time as the sand was deposited by wind and therefore cannot hold anything heavy like coins or gold. Searching an area between dunes and at the edge may yield some results if the area is water deposited sand, like after a storm or hurricane/typhoon. As the wind shifts the sand it may expose finds that were deposited by wave action.
I suggest you view the website thegoldenolde.com for more info on this topic. Norm is dead now but his site has information that is timeless.
Cheers from your pal in Bermuda,
BDA