The depth reading on my Humminbird 525 constantly flashs a different depth. In fairly shalow water, say 5 - 10 feet, it will flash between 4 and 8 feet, so it is almost impossible to tell what the depth really is. It does this all the time, whether I am moving or not. It is flasing really fast - several times a second. Any ideas on how to fix it? I have tried lowing sensitivity, but that has not helped. Any ideas are welcome. Thanks

Try to increase surface clutter setting. (TVG). Be sure that You are in advanced mode. You can choose "advanced" or "normal" mode in Setup menu tab in "User Mode" item. "Surface clutter" item You can find in "Sonar" main menu tab.
You must increase surface clutter setting (higher number) to 8 or 9 for example because You fishing in very shalow water.

Good luck
Srdjan

JMC,
what you are describing is usually the transducer installation.
First thing you need to do is goto the setup menu and restore your factory defaults. This will make sure there are not settings that are causing this. You did not say where the ducer was installed. I have seen this problem a lot with in-hull installations where air bubbles are present.
Give me a little more information.

That could be the problem. There was a Humminbird installed before I put this one in that the owner said was operating fine, and that he thought it was the 525. I bought a new 525 and did not install the transducer, but I am hoping to use the old transducer. It is an in hull installation. All the connections fit, so I was hoping to use the old transducer. I'll try going back to factory settings, but I'm pretty sure it was acting up when I first installed it and was using the factory settings. It sound like I need to reinstall the transducer. Any other options?