For beach hunting, about 50-70% of the time when you loose a signal it is because the target has sunk lower in the hole beyond detector range. This often happens when you have the scoop slightly ahead of the target and when you extract the scoop, the target, located behind the scoop, falls further down the hole out of range. This happens much more in sand than dirt, because the sand hole tends to fill-in, esp in the water. In a small portion of time, a corroded target will appear larger and detectable, because of the corrosion surrounding the target has spread out. When you disturb the ground/sand the corrosion dissipates leaving a smaller target that doesn't reach detection level. Also, esp in water, small light targets like aluminum, will blow away or float away after being uncovered. Finally, just weird stuff happens on the beach - I was about to dig a target in the water when the target swam away! I have detected a hook in a flounder at the bottom and when my scoop approached, the fish swam away with the target.