284a Diving Adventures; Instant Cities; Unconquered Amazon

This show goes to great depths: A diving enthusiast highlights the underwater world, from the turquoise coasts of Central America to the cold jade waters of Puget Sound. Then NPR's Steve Inskeep explains what Karachi showed him about the world's mushrooming mega-cities. And author Scott Wallace describes his trek deep into the Amazon, and the efforts to protect the fierce Arrow people from contact with the outside world.