By John D. Sutter, CNN
Camden, Maine (CNN) -- Follow Daniel Kish out onto a dock and ask him about the view.
"There's this pylon here and there's an object about 20 feet away -- here -- and another one, about 50 feet away," says Kish, overlooking a bay in coastal Maine during the recent PopTech conference, where he was a featured speaker. "I guess those are boats. I can't tell from this distance, really, but they're solid and we're on the water -- so it stands to reason."
Kish is completely blind -- he lost sight in both eyes by age 13 months. Yet he uses his ears to see. When he walks around unfamiliar places -- he loves hiking -- he clicks his tongue and then listens as that sound bounces off nearby objects.