recovering or testing shallow sea bottom for coins

Thinking of some easily dragged piece of equipment that could pass over surface of fairly shallow shore bottom with the idea of causing a one to two inch depth of surface to be drawn into a metal lattice enclosure.  The sand and mud would travel on through the lattice and would allow the retention of any coins or small objects to remain.  Could be drug behind any fishing boat with mechanism to disengage if struck an immovable object...but yet allow for it's recovery. Has anyone come up with such an idea?

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I am thinking a dredge is bigger.  I am thinking something smaller, able to be drug behind an ordinary fishing boat...something to "sample" the first inch or so of the bottom, in a narrow way.  I may be way off base....but I am wondering if it can be done. Or has been done.
eyepatch

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Thanks for this reply.  I had come up with the idea of a kind of rolling pin, the ends of which would be extended with a rather wide tire or wheel, that would ride on the surface of the sand.  The wheels would have several long spikes that would dig into the dirt.  As it is pulled, the long spikes would turn the rolling pin, covered with smaller spikes that would dig into the dirt or sand, and push it into the wire or lattice basket....passing on through, but sifting out any coins.  Sounds kind of far fetched. But imagine a metal rolling pin covered with small spikes, with a metal wheel on each end, covered by longer, more robust spikes that when dragged would turn the rolling pin, digging into the surface...and throwing the mud or sand into the wire or metal lattice basket.  It would have to be weighted from behind to keep it level as it is pulled.  Or better still, instead of the lattice on the top surface, attach a cap extended into a suction appartus to bring it to the surface to be sifted through a screen. More ways to skin the cat.
eyepatch

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