The Multi Kruzer only operates on one frequency at a time. The Equinox is true multifrequency, which is what you want in salt water. The other single frequency machines and PI's that claim they work in salt water, are not totally honest about it. Sure, they work, but, you have to detune them to the point where you lose lots of depth, especially in mineralized ground (I.E. black sand) None of the PI's currently have true iron discrimination. Some have a pseudo-disc that can help a bit, but, not near as good as a multifrequency VLF. Most of the PI machines I've handled are not light or ergonomic in any sense of the word. Swing a few and you will see what I'm talking about. The ATX is HEAVY. If you're going to hunt out of the water as well as in the water, you're going to want one that doesn't kill your arm after an hour of hunting. The Nox is the lightest salt water machine out there at the moment. It makes hunting the sand a true pleasure. Hip mounting an Excal is pretty nice too. The CZ21 is a very good water machine also, but, it feels awkward on the beach to me.