I recently made a StoryMap that illustrates the deepness of Challenger Deep using some comparisons. Like taking a walk through Manhattan. Or skydiving. Or free-diving. There are also the obligatory Everest, Grand Canyon and Burj Khalifa units in there, too. As one does.
Also, to keep it somewhat sciency, I have this introduction thing to the geologic formation of Challenger Deep to give context for why its so deep.
So check it out of you have five or ten minutes to burn.