Whether or not a coil is waterproof or water resistant is dependent on the design and manufacturing (molding) process. Not the series of detector. The difference between a coil being waterproof or water-resistant has more to do with external water pressure than simply being in a "water-tight" compartment. Throughout the entire Minelab lineup, you will find a mix of waterproof and water-resistant coils, again depending on the design process. For example, the X-TERRA elliptical is of the same design as the elliptical Goldsearch coil, both of which are water-resistant. The 11-inch Pro style coils, as used on the ETRAC, is fully waterproof. Unfortunately, getting that size and design to work with the X-TERRA has not been successful. But trust me, it is not because they've not made the effort. As the technology of coil development advances, we will likely see less of water-resistant coils and more waterproof coils. Case in point.....the CTX 3030, which not only has waterproof smart coils, but is an entirely waterproof detector. (again, up to a certain depth, due to external water pressure limitations) But for the time being, coils of one design are either catagorized as waterproof or water-resistant, based on design. And if you take a look at Minelab's website, you'd find that the same "classification" follows across the various models they represent, regardless of the cost of the detector they work with. JMHO HH Randy