most of the lower end (cheaper priced) preset ground balance machines tend to have issues around wet beach sand / saltwater -- since the higher mineral content is above the normal "adverage" preset "normal soil" range that the machines are set up to work at -- this tends to cause a lot of falsing -- with a preset ground balance type of maschine the only real way to attempt to deal with high mineral areas (as well as close by power lines and emf sources) is to lower the sensivity level until it no longer picks up the back ground mineral / emf / power source (basically rebalancing it via dropping the sensivity levels so that the machine now gets along with the soil / local conditions )- sadly since your not pushing as much "power" depth will suffer somewhat.--some places are so bad with high mineral content / emf that nothing short of a manually ground balancible machine will do .