Well, I was on the fence about sending my 4 month old At Pro in for the upgrade, but it made the decision for me. I was at the beach yesterday and for the first time I submerged the control unit while detecting in waist deep water. 30 seconds later, it shut off and would not come back on. A few minutes after that, there was water visible under the screen. Good news - I called Garrett and they told me to send it in for service. No questions asked. Worse part of it all is that I have to wait a few weeks to get back my serviced machine with an improved shaft locking system and a two-year extended warranty. Could have been much worse...