In a second-floor windowless room on the rundown Carl Hayden Community High School campus, four students huddle around an odd, 3-foot-tall frame constructed of PVC pipe. At the top sits a black, waterproof briefcase containing a nest of hacked processors, minuscule fans, and LEDs. It's a cheap but astoundingly functional underwater robot capable of recording sonar pings and retrieving objects 50 feet below the surface. The four teenagers who built it are all undocumented Mexican immigrants who came to this country through tunnels or hidden in the backseats of cars. But over three days last summer, these kids from the desert proved they are among the smartest young underwater engineers in the country. Read on to hear their story.