While I'm not familiar with your beaches in central ill. I can say that from my experience here in Wisconsin that we have a lot of black sand and iron rich rocks that seem to be around a lot of water here. At best it makes detecting tough in those situations. If you have a setting for salt water, try that, it may help. Also, run your sensitivity really low. That will minimize falsing, and keep the coil from blinding itself. Imagine headlights in thick fog with the high beams reflecting back at you. Same concept with coil signals in mineral rich areas.