This is a documentary about a boy (Ben Underwood) who has taught himself to use echo location to navigate around the world. Ben Underwood is blind, but has managed to do some truly extraordinary feats.
Echolocation, also called biosonar, is the biological sonar used by several animals such as shrews, most bats, and most cetaceans. The term was coined by Donald Griffin, who was the first to conclusively demonstrate its existence in bats. Two bird groups also employ this system for navigating through caves, the so called cave swiftlets in the genus Aerodramus (formerly Collocalia) and the unrelated Oilbird Steatornis caripensis.
Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects in the environment. They use these echoes to locate, range, and identify the objects. Echolocation is used for navigation and for foraging (or hunting) in various environments.