This gentleman knows how to read the beach. He hunts the Florida Treasure Coast beaches. These two videos are packed with good info. Note: he swings in an arc due to wrist injuries.
More on the history of Florida’s Treasure Coast Beach
And here is why the coins get eventually washed up on the beaches after storms. Because the Treasure Coast Spanish Fleet shipwrecks are not far off from the beach. Notice in below video how close the recovery boat was from the beach. Note this is a leased site, you cannot dive at that site or hunt in the water, but you can hunt the beach at all tide levels legally.