The upgrade to either an AT Pro or Max and the 600 or 800 is the XP Deus. It outshines any detector made. Sometimes you can pick up a used one for the price of a new 800. The don't break, either. I had an AT Pro that broke its coil and the Equinoxes have been plagued with gremlins, which is very disappointing coming from a big name manufacturer.
Most people do however, in one respect or another. Even if you never go to the ocean, or hunt lakes or rivers, you'll probably have to cross a creek sometime, or you simply get caught in a downpour some distance from shelter. Being waterproof should be a basic feature with all good detectors these days. That hokey water kit that XP will sell you for the Deus is laughable.