Only THREE Waterbending Nations?

Am I the only one who thinks that it's crazy that there are only three waterbending nations in the whole world? One of them even lives in secret, unknown to the rest of the world.

Thank goodness for the Roku novel showing that there were other small groups of benders around. I hope that we get more information on other waterbending nations in future novels, because I believe that there HAS to be more than just three in the world.