sorry for slow reply - I missed you question - I dig just 1-2 meters below the surface looking for the gravel layers from ancient river beds - these can be hundreds of feet above ground water - I research the areas to dig and test a small area for a half day -then work it hard for around a 4-7 days = if you want some uncut or cut sapphires I will sell you a parcel very cheap
if you want to know where to go I can give you some hints too

This aquamarine is mined well below ground in a mountain side mine in Nepal -- I was lucky to buy it