This is from the rocks section of the Tutorial. From within Chart Trainer, you just click any of the boxed rock symbols to read details of its meaning and interpretation. Rocks are also described with numerous photos in other parts of the program and discussed in deail in the Chart Manual section.
There are eight (8) different kinds of rock symbols shown above, which differ significantly in what they mean and in what we would see when viewing them (or not viewing them) on the water. Do you know these distinctions?