I would like to know why simultaneous multifrequency detectors are the rage at this time. I would prefer responses from electrical engineers or designers of metal detectors. Why, when the Fisher CZ series came out, did they not "obsolete" their competitors, why are the new ones so much better than the CZ series, and why are they so much better than anything else. I am pretty sure they are better in salt water and would like to know why. I would also appreciate it if people who own both smf and single frequency detectors would reply. I would not appreciate remarks about how mine is better than yours or proofs that come from advertising. Help me out!