You take the gear needed for the mission.

And for Marine Staff Sgt. Adam Jacks – a company gunnery sergeant at The Basic School at Quantico, Va. -- that means selecting the correct prosthetic leg. He has about 20 prosthetics, to include a few specifically designed for tasks most observers would not expect an amputee to accomplish.

Jacks has one prosthetic leg that helped him become the first amputee to conquer the Marine Corps' Combat Instructor of Water Survival course. Another prosthetic allows him to run routes as a wide receiver on a semi-pro football team in Fredericksburg, Virginia.

"It just takes a lot of patience, I guess – that and trying to figure out a better way to do things," Jacks said in explaining his accomplishments.

Jacks, 28, lost his right leg at mid-thigh to an improvised explosive device blast in April 2011. He also incurred a minor traumatic brain injury.

In order to stay on active duty in the Marine Corps, Jacks needed the commandant of the Marine Corps to grant him expanded permanent limited duty status. Gen. James Amos, then the commandant, told Jacks he wouldn't "push him out" of the Corps and Jacks received the waiver.

Jacks is not the first service member to stay on active duty after sustaining an injury that once would have led to medical retirement. Advances in prosthetics and military leadership increasingly seeing the utility of retaining seriously injured troops has offered more opportunities to amputees.

An Ohio native, Jacks has served in the Marine Corps for a decade and plans to reach at least 20 years. Jacks has set lofty goals since he lost his leg and continues to strive to accomplish them.

Last November he was one of six Marines to successfully complete the Marine Combat Instructor Water Survival course that required him to swim 59 miles over three weeks.

"Swimming to me was always recreational," he said. "It's something I wanted to do years ago but never was really sure until I was approached by a gunnery sergeant friend of mine."

Gunnery Sgt. Joseph Marshall, then the chief instructor for the course, urged his friend to take on the challenge despite missing his right leg.

"There was some doubt on my part – depending on how mentally and physically challenging the course was," Jacks said. "I was worried about prosthetics – would they be able to help me out. But in talking to him for a few minutes he just said, 'C'mon, try it out.' "

He and his fellow NCO modified his "water leg" by adding some foam to it and fixing it in place with duct tape. On the prosthetic foot there is a swim fin.

"There's not a good upbeat or downbeat when you kick your leg in the water for that good ripping effect or wave effect, if you know what I mean," he said. The foam helped him to stay buoyant. Even if it did not aid in the actual swimming, "it was better than nothing," Jacks said.

"We tried to master some kind of technology for me to be in the water. It was a lot of trial and error, a lot of time in the pool. Finally we decided I would just swim the course entirely upper body," he said.

Marshall, interviewed by Marine public affairs in November, said Jacks put in dozens of extra training hours to achieve proficiency, at times staying at the pool up to two hours after the other students had left for the day.

Requirements included swims up to 1,900 meters and well as 25-meter underwater swims. Jacks also had to complete eight American Red Cross rescues -- four with lifesaving equipment and four without --and pass all academic classroom evaluations.

"We were not going to lower the standard," Marshall said. "We were going to work with him to help him reach it."

Jacks not only refused to let his disability slow him down in the pool. The Marine also has returned to the football field.

Another fellow Marine encouraged Jacks to try out for the Fredericksburg Bears, a semi-pro football team about 25 miles south of Quantico. He went down to meet the team and its coach, Rod Anderson.

"I said okay, let me reach out to the league to see if they have any objections," Anderson recalled. "The league came back unanimously and said 'absolutely not [a problem]." He showed up [to try out]. He had a great attitude. He was all in."

"We go full pads in practice. He's doing his thing out there like anyone else. It's pretty awesome actually, it's a motivator. Some guys are younger than him and with full use of their limbs and don't work as hard."

Anderson said Jacks "has played every game thus far. No catches yet but a key block in our first win. He's a stud."

-- Bryant Jordan can be reached at bryant.jordan@military.com