A Little History...
The story of the National Association of Underwater Instructors (NAUI) begins in 1959 with a shared vision of what quality scuba training should be and a commitment to "Dive Safety Through Education."
So really, why?
NAUI trains US Astronauts. NASA's Neutral Buoyancy Lab, NBL, where astronauts are trained to perform tasks in a zero-g environment is run by NAUI staff using NAUI standards.
US Navy -
NAUI trains US Navy SEALS. The U.S. Navy, including the NAVY SEALS, use NAUI standards and teaching methods to train sailors.