The new Navy SEAL 4221.BO.NSF.SET Series is designed from our 4200 ANU (Authorized Navy Use) series in collaboration with the NSF. In World War II, during the era of Frogmen and beach landings under fire, if a piece of diving gear wasn’t on the ANU list, you didn’t use it. In the early 1960s these Frogmen evolved into the most elite maritime commandos – the U.S. Navy SEALs. The ANU list of equipment provided these Frogmen of the past and the Navy SEALs today with a sense of security that their gear would work when needed. It is with this same intent that we developed these watches and the effort resulted in a watch that functions perfectly in any environment, having performed under the toughest conditions and in the harshest environments.