Keywords: US Navy 110920-N-YO394-142 A visitor from the U.S. Air Force Air War College tries on a MK-21 diving helmet during a visit to Navy Expeditionary Co.jpg en VIRGINIA BEACH Va Sept 20 2011 A visitor from the U S Air Force Air War College tries on a MK-21 diving helmet during a visit to Navy Expeditionary Combat Command NECC Students at the school visited NECC to familiarize themselves with the capabilities the command brings to the joint warfighter U S Navy photo by Mass Communication Specialist 2nd Class Paul D Williams/Released 2011-09-20 110920-N-YO394-142 Navy http //www navy mil/view_image asp id 107561 U S Navy photo by Mass Communication Specialist 2nd Class Paul D Williams PD-USGov-Military-Navy Naval Amphibious Base Little Creek MK-21 diving helmet |