Resistivity testing is a tried and true method for helping to find groundwater, but this device will not reliably locate water more than a meter or two down unfortunately. And even if you had higher powered unit with enough sensitivity to get readings at more than 20+ feet, it actually takes quite a bit of training to interpret the results as the data can be effected by various factors which, if not accounted for, would give you a lot of false positives.
Did Steve tell you that? Fuh - Steve. Just look at this tiny ad: