I've got a Humminbird 525 depth finder and when I'm in about 4 ft of water or less it shows .6 ft depth.  Anyone ever had a similar problem or know what could be wrong?  I find myself checking the depth with my rod rather than my depth finder:).

Check your settings for "depth offset".  You can compensate for the depth of your transducer with this setting.  If your transducer is two feet below the surface you can set it to -2 feet to get accurate readings.

If that isn't screwed up turn down your sensitivity and see if that helps.