Humminbird RF25 SmartCast Advanced Pole Mount Sonar?

I want to buy a depth finder/fish finder for my kayak, but I would prefer portable one with internal batteries.   I found the Humminbird Smartcast series, and I was curious is it any good?   The only down side I can see is that 120 feet is the max depth.    Let me know what you guys think of this unit or if you have any experience with any other portable depth finders.  Thank you!

Here's a link to the Humminbird RF25 SmartCast Advanced Pole Mount Sonar:

http://www.walmart.com/ip/Humminbird-RF25-SmartCast-Advanced-Pole-Mount-Sonar/13437607