In some cases, these drills offer many advantages.
Most of the manufacturers of these mini-drills advertise their drills are capable of drilling to 200 feet. Realistically, however, they operate best at less than 100 feet. Some are built with larger engines (these are called commercial models), however, inexperienced operators should limit their drilling to less than 100 feet, at least until they gain some drilling knowledge and experience. I've drilled as deep as 300 feet with these 200-foot mini-drills, but this is for only very experienced operators. I've successfully drilled wells with these mini-drills in sands, clays, coral and rock, but most of these drills should be limited to sands and clays.