Diving with robots and astronauts - [Back Story]

IEEE spectrum contributing editor Evan Ackerman is a veteran scuba diver who has played fetch with sea lions in the Galápagos, spotted an elusive mimic octopus in Indonesia, and been run over by a bull shark in Fiji. But on his most recent dive trip, Ackerman had a chance to swim with some of the rarest underwater creatures on Earth: astronauts.