i-Boating relief shading is like Google Street View, but for underwater terrain (Sea View). It's a visual representation of what the underwater terrain looks like. If you were to drain the oceans/lakes of all the water, that is the kind of view relief shading attempts to show. Here is what the terrain looks like off the coast of Marblehead, MA. This is what the bottom of Lake Powell looks like. This is what the bottom of Lake Tahoe looks like. This is what the bottom of Smith Mountain Lake looks like.

 The i-Boating app includes detailed lake temperature maps, accurate to 1 degree Fahrenheit( 0.5 degree celsius approx). Using it you can identify where all the warm zones are, where the temperatures are changing. More importantly you can cross reference this information with structure data to narrow  down the most productive areas. Here you can clearly see that Florida lakes are warming up. Lake Temperature Maps