cell phone chart for Florida Keys?

[serpa4]

So, heading to the keys and taking the toon for a 7 day trip. I've never boated in the keys before where the water is shallow. I'd like to take some type of moving chart with me for GPS navigation. I'll just be boating around to the different islands and snorkeling. Since I don't have a need for charts other than this time out, I was thinking of using my Galaxy Note 2 phone for my GPS device since it has a very larger battery and a 5.5" screen which is bigger than some chart plotters. So, what I'm looking for, if it exists, it something like google maps that just shows the channels I should stay in and the depth of the water I'm boating in ahead of time. I have a depth finder, but want to know if I'm approaching low spots by looking at my screen before I get to any possible low areas.
Anyone have experience with maps/charts for Android devices?

[Ron Burgundy]

Navionics app. $10 and is exactly what you're looking for. Even if you get out of cell tower range it still works off the gps satellites.

[rbiederwolf]

+1 on Navionics. I navigated my entire Keys trip last summer