HARI SREENIVASAN:

Half a mile off the Florida Keys, a small boat of scientists is confronting a vast underwater crisis.

Biologists David Vaughan, Christopher Page, and Rudiger Bieler are attempting lifesaving transplants for Florida's coral reefs, which are dying at alarming rates.

BILL CAUSEY, NOAA Office of National Marine Sanctuaries: This is America's only living barrier coral reef here in the Florida Keys, and it is in a perilous state at this point in time.