NY: At the bottom of a swimming pool a group of men voluntarily sink with their hands bound behind their backs after instructed to reach their face masks on the floor using only their teeth.
There appears little struggle as the men calmly work to complete their task before the next one is issued, most likely making their challenge even harder, but all in a day's training.
These are the United States' unsung heroes, the Navy SEALS, an exclusive band of about 2,400 special operators most famously responsible for the 2011 midnight raid that led to the capture of Osama bin Laden.
'They are America's James Bonds,' Greg Mathieson recently told Fox News of these elite men he's spent the last six years researching and photographing.
They, as well as all other members of special warfare - with there being he says about 20 support personnel for every Navy SEAL out there - appear in his new book: United States Naval Special Warfare.
'They have so much gadgets and equipment, the skill level of these guys, an average SEAL out there, has a degree in college. He may speak a couple different language,' Mr Mathieson emphasized.
The result of Mr Mathieson's alongside field work is a stunning 931 photograph collection, some exclusive and never-before seen, that he's never been granted permission to release until now.
Some chapters are even written by the SEALS themselves.
'No one's ever done a book that shows everything they do,' Mr Mathieson said. 'They only show bits and piece of them over the years but no one has ever done the entire history and this goes back to WWII, all the way up to the future.'
That future refers to outlines of new concepts and prototypes currently under development.
One such seen in his book is a drawing of the Marion Hyper-sub prototype Fathom.
It's an undersea vehicle capable of carrying up to eight personnel to depths of 600 feet while traveling 1,000 miles without having to refuel.
Some gadgets from the past he uncovered, specifically 1961 and 1962, also proved most remarkable - even if never used.
‘The most amazing was the SADM, Strategic Atomic Demolition Munition,’ he told NBC.
‘This was a 160-pound atomic bomb that was the size of a basketball. It had an underwater casing that SEALs would tie to their chest, jump out of planes and then place wherever ordered.
‘Think about it, this was long before micro-circuitry and the advances we take for granted today. It existed, but the SADM was never used,’ he said.
'I tried to start this [project] 30 years ago when I was in Honduras and I met a SEAL,' Mr Mathieson told NBC of his project’s inspiration.
'I wrote a letter to Adm. George Worthington back then and was denied complete access. Fast forward and Adm. Worthington had retired, but we had stayed in touch. He opened doors because he saw this was a story that really should be told and with that, I had access,' he said.
Today his 403-page book opens with an introduction by President George W Bush and a foreword by Secretary of the Navy and 9-11 Commission member John Lehman.
'It took a lot of getting to know all the right people,' he admits to Fox.
'Because of unparalleled access given the author and photographers, this book has insights behind the scenes of the support personnel, unique training, underwater vehicles, operations in Iraq and Afghanistan, unique weapons developed just for the SEALs as well as into the future of Naval Special Warfare (NSW) written by Secretary of the Navy Donald Winter,' the book states.
