Up until last Sunday my ATPro with a 504 serial number worked great. I thought I had missed the bullet on problems. Sunday before last I spent 3 - 4 hours in a fresh water lake and found some clad, junk jewelry and the usual junk. When I went back this last Sunday, it started being erratic as soon as I got into the water, and I could only use it in the STD Custom mode. I got a lot of spurious signals and a bunch of targets I couldn't find. Ended up finding one nickel and some pull tabs in about 3 hours. Called Garrett and sent it back. It had batteries with only the 3 - 4 hours from the previous week on them and I tried everything I could think of including setting it back to default. I even tried more new batteries. I didn't see any water in the battery compartment or behind the display. I still like the machine, and plan to take it to England in September. I'm philosophical about the problem, as right at this time, I don't have a lot of time to hunt and we've been in a drought with the temperature being over 90 degrees over half of the days in the last month. Ground is hard. So, if it had to happen, now is a good time for it. Skip