How do tides affect gravel /sand beaches? I've been doing some hunting on the Delaware river and had some success. I dug a deep hole for the hell of it as a test at low tide, the next day the was no evidence of the hole, plus I found a coin that I didn't get a signal from the day before. Can older coins (pre 1900) that are 6+ inches move up to signal range with the movement of the tides?
Water will sort it out after weight so coins will probably go deeper, like a sluice box seperates concentrates(heavier then normal sand) the water will move the sand at the beach to, probably metal objects to.
It is important to understand that the beach is always changing. Waves, currents, storms, wind and rain can dramatically change beach geography. Buried objects behave predictably in this environment. Most metal objects are denser than the surrounding sand and will bury themselves deeper and deeper over time. The beach actually vibrates due to the pounding surf which accelerates this process. Objects will continue to sink until they come to rest upon a denser surface. This could be a layer of gravel or clay. The point here is that you want to look for areas of the beach that have had a lot of sand removed. If you see gravel or clay, or deep cuts in the sand, then you would want to hunt those areas. Objects also migrate along the beach. A current washing along a beach will deposit objects of similar density in the same place. This will result in a line of objects varying from lightest to heaviest along the beach. If you pay attention to the trash items deposited by the current and look for the heavier objects there is a good chance valuable items will be in the same place.
The beach is subject to other phenomenon, namely tides and wind. During low tide, areas that were deep water are now shallow and shallow water is now wet sand. This allows you to get farther out and hunt areas that are difficult to hunt at any other time. There are a few times a year that the tides are very low. They are called minus tides. If you can time your trip for one of these tides you will find that you can venture out much farther than at any other time of the year. Wind can lower the water level if it is blowing out to sea. If you can hit the beach during a minus tide with the wind blowing out to sea, do not miss the chance to do so.