The old Kodak box instructions that said to have the sun behind you should be discarded! Backlight gives definition, and you don't have Uncle Harry or Baby Mark squinting like crazy at you. But keep in mind that bright, specular reflections on the water will throw your in-camera metering system off-balance, and you will need to open up/increase exposure to compensate. And give your subject "room to look;" in the above there is more room in front of the child than behind. It also illustrates "the rule of thirds..."